|
Study / report
title, author, and year published |
Predominant
finding on natural immunity |
|
1)
Necessity of COVID-19 vaccination in previously
infected individuals, Shrestha, 2021 |
"Cumulative
incidence of COVID-19 was examined among 52,238
employees in an American healthcare system. The
cumulative incidence of SARS-CoV-2 infection
remained almost zero among previously infected
unvaccinated subjects, previously infected
subjects who were vaccinated, and previously
uninfected subjects who were vaccinated,
compared with a steady increase in cumulative
incidence among previously uninfected subjects
who remained unvaccinated. Not one of the 1359
previously infected subjects who remained
unvaccinated had a SARS-CoV-2 infection over the
duration of the study. Individuals who have had
SARS-CoV-2 infection are unlikely to benefit
from COVID-19 vaccination..." |
|
2)
SARS-CoV-2-specific T cell immunity in cases of
COVID-19 and SARS, and uninfected controls,
Le Bert, 2020 |
"Studied T cell
responses against the structural (nucleocapsid
(N) protein) and non-structural (NSP7 and NSP13
of ORF1) regions of SARS-CoV-2 in
individuals convalescing from coronavirus
disease 2019 (COVID-19) (n = 36). In
all of these individuals, we found CD4 and CD8 T
cells that recognized multiple regions of the N
protein... showed that patients (n = 23)
who recovered from SARS possess long-lasting
memory T cells that are reactive to the N
protein of SARS-CoV 17 years after the outbreak
of SARS in 2003; these T cells displayed robust
cross-reactivity to the N protein of
SARS-CoV-2." |
|
3)
Comparing SARS-CoV-2 natural immunity to
vaccine-induced immunity: reinfections versus
breakthrough infections,Gazit, 2021 |
"A retrospective
observational study comparing three groups: (1)
SARS-CoV-2-naïve individuals who received a
two-dose regimen of the BioNTech/Pfizer mRNA
BNT162b2 vaccine, (2) previously infected
individuals who have not been vaccinated, and
(3) previously infected and single
dose vaccinated individuals found para a 13 fold
increased risk of breakthrough Delta infections
in double vaccinated persons, and a 27 fold
increased risk for symptomatic breakthrough
infection in the double vaccinated relative to
the natural immunity recovered persons... the
risk of hospitalization was 8 times higher in
the double vaccinated (para)... this analysis
demonstrated that natural immunity affords
longer lasting and stronger protection against
infection, symptomatic disease and
hospitalization due to the Delta variant of
SARS-CoV-2, compared to the BNT162b2 two-dose
vaccine-induced immunity." |
|
4)
Highly functional virus-specific cellular immune
response in asymptomatic SARS-CoV-2 infection,
Le Bert, 2021 |
"Studied
SARS-CoV-2–specific T cells in a cohort of
asymptomatic (n = 85) and symptomatic (n =
75) COVID-19 patients after seroconversion...
thus, asymptomatic SARS-CoV-2–infected
individuals are not characterized by weak
antiviral immunity; on the contrary, they mount
a highly functional virus-specific cellular
immune response." |
|
5)
Large-scale study of antibody titer decay
following BNT162b2 mRNA vaccine or SARS-CoV-2
infection, Israel, 2021 |
"A total of 2,653
individuals fully vaccinated by two doses of
vaccine during the study period and 4,361
convalescent patients were included. Higher
SARS-CoV-2 IgG antibody titers were observed in
vaccinated individuals (median 1581 AU/mL IQR
[533.8-5644.6]) after the second vaccination,
than in convalescent individuals (median 355.3
AU/mL IQR [141.2-998.7]; p<0.001). In vaccinated
subjects, antibody titers decreased by up to 40%
each subsequent month while in convalescents
they decreased by less than 5% per month... this
study demonstrates individuals who received the
Pfizer-BioNTech mRNA vaccine have different
kinetics of antibody levels compared to patients
who had been infected with the SARS-CoV-2 virus,
with higher initial levels but a much faster
exponential decrease in the first group". |
|
6)
SARS-CoV-2 re-infection risk in Austria,
Pilz, 2021 |
Researchers
recorded "40 tentative re-infections in 14, 840
COVID-19 survivors of the first wave (0.27%) and
253 581 infections in 8, 885, 640 individuals of
the remaining general population (2.85%)
translating into an odds ratio (95% confidence
interval) of 0.09 (0.07 to 0.13)... relatively low
re-infection rate of SARS-CoV-2 in Austria.
Protection against SARS-CoV-2 after natural
infection is comparable with the highest
available estimates on vaccine
efficacies." Additionally, hospitalization in
only five out of 14,840 (0.03%) people and death
in one out of 14,840 (0.01%) (tentative
re-infection). |
|
7)
mRNA vaccine-induced SARS-CoV-2-specific T cells
recognize B.1.1.7 and B.1.351 variants but
differ in longevity and homing properties
depending on prior infection status,
Neidleman, 2021 |
"Spike-specific T
cells from convalescent vaccinees differed
strikingly from those of infection-naïve
vaccinees, with phenotypic features suggesting
superior long-term persistence and ability to
home to the respiratory tract including the
nasopharynx. These results provide reassurance
that vaccine-elicited T cells respond robustly
to the B.1.1.7 and B.1.351 variants, confirm
that convalescents may not need a second vaccine
dose." |
|
8)
Good news: Mild COVID-19 induces lasting
antibody protection, Bhandari, 2021 |
"Months after
recovering from mild cases of COVID-19, people
still have immune cells in their body pumping
out antibodies against the virus that causes
COVID-19, according to a study from researchers
at Washington University School of Medicine in
St. Louis. Such cells could persist for a
lifetime, churning out antibodies all the while.
The findings, published May 24 in the journal
Nature, suggest that mild cases of COVID-19
leave those infected with lasting antibody
protection and that repeated bouts of illness
are likely to be uncommon." |
|
9)
Robust neutralizing antibodies to SARS-CoV-2
infection persist for months, Wajnberg, 2021 |
"Neutralizing
antibody titers against the SARS-CoV-2 spike
protein persisted for at least 5 months after
infection. Although continued monitoring of this
cohort will be needed to confirm the longevity
and potency of this response, these preliminary
results suggest that the chance of reinfection
may be lower than is currently feared." |
|
10)
Evolution of Antibody Immunity to SARS-CoV-2,
Gaebler, 2020 |
"Concurrently,
neutralizing activity in plasma decreases by
five-fold in pseudo-type virus assays. In
contrast, the number of RBD-specific memory B
cells is unchanged. Memory B cells display
clonal turnover after 6.2 months, and the
antibodies they express have greater somatic
hypermutation, increased potency and resistance
to RBD mutations, indicative of continued
evolution of the humoral response... we conclude
that the memory B cell response to SARS-CoV-2
evolves between 1.3 and 6.2 months after
infection in a manner that is consistent with
antigen persistence." |
|
11)
Persistence of neutralizing antibodies a year
after SARS-CoV-2 infection in humans,
Haveri, 2021 |
"Assessed the
persistence of serum antibodies following WT
SARS-CoV-2 infection at 8 and 13 months after
diagnosis in 367 individuals... found that NAb
against the WT virus persisted in 89% and S-IgG
in 97% of subjects for at least 13 months after
infection." |
|
12)
Quantifying the risk of SARS-CoV-2 reinfection
over time, Murchu, 2021 |
"Eleven large
cohort studies were identified that estimated
the risk of SARS-CoV-2 reinfection over time,
including three that enrolled healthcare workers
and two that enrolled residents and staff of
elderly care homes. Across studies, the total
number of PCR-positive or antibody-positive
participants at baseline was 615,777, and the
maximum duration of follow-up was more than 10
months in three studies. Reinfection was an
uncommon event (absolute rate 0%–1.1%), with no
study reporting an increase in the risk of
reinfection over time." |
|
13)
Natural immunity to covid is powerful.
Policymakers seem afraid to say so, Makary,
2021 |
Makary writes
"it's okay to have an incorrect scientific
hypothesis. But when new data proves it wrong,
you have to adapt. Unfortunately, many elected
leaders and public health officials have held on
far too long to the hypothesis that natural
immunity offers unreliable protection against
covid-19 - a contention that is being rapidly
debunked by science. More than 15 studies have
demonstrated the power
of immunity acquired by previously having
the virus. A 700,000-person study from
Israel two weeks ago found that those who had
experienced prior infections were
27 times less likely to get a second symptomatic
covid infection than those who were vaccinated.
This affirmed a June Cleveland Clinic study of
health-care workers (who are often exposed to
the virus), in which none who
had previously tested positive for the coronavirus got
reinfected. The study authors concluded that
"individuals who have had SARS-CoV-2 infection
are unlikely to benefit from covid-19
vaccination." And in May, a Washington
University study found
that even a mild covid infection resulted in
long-lasting immunity." |
|
14)
SARS-CoV-2 elicits robust adaptive immune
responses regardless of disease severity,
Nielsen, 2021 |
"203 recovered
SARS-CoV-2 infected patients in Denmark between
April 3rd and July 9th 2020,
at least 14 days after COVID-19 symptom
recovery... report broad serological profiles
within the cohort, detecting antibody binding to
other human coronaviruses... the viral surface
spike protein was identified as the dominant
target for both neutralizing antibodies and CD8+ T-cell
responses. Overall, the majority of patients had
robust adaptive immune responses, regardless of
their disease severity." |
|
15)
Protection of previous SARS-CoV-2 infection is
similar to that of BNT162b2 vaccine protection:
A three-month nationwide experience from Israel,
Goldberg, 2021 |
"Analyze an
updated individual-level database of the entire
population of Israel to assess the protection
efficacy of both prior infection and vaccination
in preventing subsequent SARS-CoV-2 infection,
hospitalization with COVID-19, severe disease,
and death due to COVID-19... vaccination was
highly effective with overall estimated efficacy
for documented infection of 92·8% (CI:[92·6,
93·0]); hospitalization 94·2% (CI:[93·6, 94·7]);
severe illness 94·4% (CI:[93·6, 95·0]); and
death 93·7% (CI:[92·5, 94·7]). Similarly, the
overall estimated level of protection from prior
SARS-CoV-2 infection for documented infection is
94·8% (CI: [94·4, 95·1]); hospitalization 94·1%
(CI: [91·9, 95·7]); and severe illness 96·4%
(CI: [92·5, 98·3])... results question the need
to vaccinate previously-infected individuals." |
|
16)
Incidence of Severe Acute Respiratory Syndrome
Coronavirus-2 infection among previously
infected or vaccinated employees, Kojima,
2021 |
"Employees were
divided into three groups: (1) SARS-CoV-2 naïve
and unvaccinated, (2) previous SARS-CoV-2
infection, and (3) vaccinated. Person-days were
measured from the date of the employee first
test and truncated at the end of the observation
period. SARS-CoV-2 infection was defined as two
positive SARS-CoV-2 PCR tests in a 30-day
period... 4313, 254 and 739 employee records for
groups 1, 2, and 3... previous SARS-CoV-2 infection
and vaccination for SARS-CoV-2 were associated
with decreased risk for infection or
re-infection with SARS-CoV-2 in a routinely
screened workforce. The was no difference in the
infection incidence between vaccinated
individuals and individuals with previous
infection." |
|
17)
Having SARS-CoV-2 once confers much greater
immunity than a vaccine - but vaccination remains
vital, Wadman, 2021 |
"Israelis who had
an infection were more protected against the
Delta coronavirus variant than those who had an
already highly effective COVID-19 vaccine... the
newly released data show people who once had a
SARS-CoV-2 infection were much less likely than
never-infected, vaccinated people to get Delta,
develop symptoms from it, or become hospitalized
with serious COVID-19." |
|
18)
One-year sustained cellular and humoral
immunities of COVID-19 convalescents, Zhang,
2021 |
"A systematic
antigen-specific immune evaluation in 101
COVID-19 convalescents; SARS-CoV-2-specific IgG
antibodies, and also NAb can persist among over
95% COVID-19 convalescents from 6 months to 12
months after disease onset. At least 19/71 (26%)
of COVID-19 convalescents (double positive in
ELISA and MCLIA) had detectable circulating IgM
antibody against SARS-CoV-2 at 12m post-disease
onset. Notably, the percentages of convalescents
with positive SARS-CoV-2-specific T-cell
responses (at least one of the SARS-CoV-2
antigen S1, S2, M and N protein) were 71/76
(93%) and 67/73 (92%) at 6m and 12m,
respectively." |
|
19)
Functional SARS-CoV-2-Specific Immune Memory
Persists after Mild COVID-19, Rodda, 2021 |
"Recovered
individuals developed SARS-CoV-2-specific
immunoglobulin (IgG) antibodies, neutralizing
plasma, and memory B and memory T cells that
persisted for at least 3 months. Our data
further reveal that SARS-CoV-2-specific IgG
memory B cells increased over time.
Additionally, SARS-CoV-2-specific memory
lymphocytes exhibited characteristics associated
with potent antiviral function: memory T cells
secreted cytokines and expanded upon antigen
re-encounter, whereas memory B cells expressed
receptors capable of neutralizing virus when
expressed as monoclonal antibodies. Therefore,
mild COVID-19 elicits memory lymphocytes that
persist and display functional hallmarks of
antiviral immunity." |
|
20)
Discrete Immune Response Signature to SARS-CoV-2
mRNA Vaccination Versus Infection, Ivanova,
2021 |
"Performed
multimodal single-cell sequencing on peripheral
blood of patients with acute COVID-19 and
healthy volunteers before and after receiving
the SARS-CoV-2 BNT162b2 mRNA vaccine to compare
the immune responses elicited by the virus and
by this vaccine... both infection and
vaccination induced robust innate and adaptive
immune responses, our analysis revealed
significant qualitative differences between the
two types of immune challenges. In COVID-19
patients, immune responses were characterized by
a highly augmented interferon response which was
largely absent in vaccine recipients. Increased
interferon signaling likely contributed to the
observed dramatic upregulation of cytotoxic
genes in the peripheral T cells and innate-like
lymphocytes in patients but not in immunized
subjects. Analysis of B and T cell receptor
repertoires revealed that while the majority of
clonal B and T cells in COVID-19 patients were
effector cells, in vaccine recipients clonally
expanded cells were primarily circulating memory
cells... we observed the presence of cytotoxic
CD4 T cells in COVID-19 patients that were
largely absent in healthy volunteers following
immunization. While hyper-activation of
inflammatory responses and cytotoxic cells may
contribute to immunopathology in severe illness,
in mild and moderate disease, these features are
indicative of protective immune responses and
resolution of infection." |
|
21)
SARS-CoV-2 infection induces long-lived bone
marrow plasma cells in humans, Turner, 2021 |
"Bone marrow
plasma cells (BMPCs) are a persistent and
essential source of protective antibodies...
durable serum antibody titres are maintained by
long-lived plasma cells - non-replicating,
antigen-specific plasma cells that are detected
in the bone marrow long after the clearance of
the antigen ... S-binding BMPCs are quiescent,
which suggests that they are part of a stable
compartment. Consistently, circulating resting
memory B cells directed against SARS-CoV-2 S
were detected in the convalescent individuals.
Overall, our results indicate that mild
infection with SARS-CoV-2 induces robust
antigen-specific, long-lived humoral immune
memory in humans... overall, our data provide
strong evidence that SARS-CoV-2 infection in
humans robustly establishes the two arms of
humoral immune memory: long-lived bone marrow
plasma cells (BMPCs) and memory B-cells." |
|
22)
SARS-CoV-2 infection rates of antibody-positive
compared with antibody-negative health-care
workers in England: a large, multicentre,
prospective cohort study (SIREN), Jane Hall,
2021 |
"The SARS-CoV-2
Immunity and Reinfection Evaluation study...
30 625 participants were enrolled into the
study... a previous history of SARS-CoV-2
infection was associated with an 84% lower risk
of infection, with median protective effect
observed 7 months following primary infection.
This time period is the minimum probable effect
because seroconversions were not included. This
study shows that previous infection with
SARS-CoV-2 induces effective immunity to future
infections in most individuals." |
|
23)
Pandemic peak SARS-CoV-2 infection and
seroconversion rates in London frontline
health-care workers, Houlihan, 2020 |
"Enrolled 200
patient-facing HCWs between March 26 and April
8, 2020... represents a 13% infection rate (i.e.
14 of 112 HCWs) within the 1 month of follow-up
in those with no evidence of antibodies or viral
shedding at enrolment. By contrast, of 33 HCWs
who tested positive by serology but tested
negative by RT-PCR at enrolment, 32 remained
negative by RT-PCR through follow-up, and one
tested positive by RT-PCR on days 8 and 13 after
enrolment." |
|
24)
Antibodies to SARS-CoV-2 are associated with
protection against reinfection, Lumley, 2021 |
"Critical to
understand whether infection with Severe Acute
Respiratory Syndrome Coronavirus 2 (SARS-CoV-2)
protects from subsequent reinfection... 12219
HCWs participated... prior SARS-CoV-2 infection
that generated antibody responses offered
protection from reinfection for most people in
the six months following infection." |
|
25)
Longitudinal analysis shows durable and broad
immune memory after SARS-CoV-2 infection with
persisting antibody responses and memory B and
T cells, Cohen, 2021 |
"Evaluate 254
COVID-19 patients longitudinally up to 8 months
and find durable broad-based immune responses.
SARS-CoV-2 spike binding and neutralizing
antibodies exhibit a bi-phasic decay with an
extended half-life of >200 days suggesting the
generation of longer-lived plasma cells... most
recovered COVID-19 patients mount broad, durable
immunity after infection, spike IgG+ memory B
cells increase and persist post-infection,
durable polyfunctional CD4 and CD8 T cells
recognize distinct viral epitope regions." |
|
26)
Single cell profiling of T and B cell
repertoires following SARS-CoV-2 mRNA vaccine,
Sureshchandra, 2021 |
"Used single-cell
RNA sequencing and functional assays to compare
humoral and cellular responses to two doses of
mRNA vaccine with responses observed in
convalescent individuals with asymptomatic
disease... natural infection induced expansion
of larger CD8 T cell clones occupied distinct
clusters, likely due to the recognition of a
broader set of viral epitopes presented by the
virus not seen in the mRNA vaccine." |
|
27)
SARS-CoV-2 antibody-positivity protects against
reinfection for at least seven months with 95%
efficacy, Abu-Raddad, 2021 |
"SARS-CoV-2
antibody-positive persons from April 16 to
December 31, 2020 with a PCR-positive swab ≥14
days after the first-positive antibody test were
investigated for evidence of reinfection, 43,044
antibody-positive persons who were followed for
a median of 16.3 weeks... reinfection is rare in
the young and international population of Qatar.
Natural infection appears to elicit strong
protection against reinfection with an efficacy
~95% for at least seven months." |
|
28)
Orthogonal SARS-CoV-2 Serological Assays Enable
Surveillance of Low-Prevalence Communities and
Reveal Durable Humoral Immunity, Ripperger,
2020 |
"Conducted a
serological study to define correlates of
immunity against SARS-CoV-2. Compared to those
with mild coronavirus disease 2019 (COVID-19)
cases, individuals with severe disease exhibited
elevated virus-neutralizing titers and
antibodies against the nucleocapsid (N) and the
receptor binding domain (RBD) of the spike
protein... neutralizing and spike-specific
antibody production persists for at least
5–7 months... nucleocapsid antibodies frequently
become undetectable by 5–7 months." |
|
29)
Anti-spike antibody response to natural
SARS-CoV-2 infection in the general population,
Wei, 2021 |
"In the general
population using representative data from 7,256
United Kingdom COVID-19 infection survey
participants who had positive swab SARS-CoV-2
PCR tests from 26-April-2020 to 14-June-2021...
we estimated antibody levels associated with
protection against reinfection likely last 1.5-2
years on average, with levels associated with
protection from severe infection present for
several years. These estimates could inform
planning for vaccination booster strategies." |
|
30)
Antibody Status and Incidence of SARS-CoV-2
Infection in Health Care Workers, Lumley,
2021 |
"12,541 health
care workers participated and had anti-spike IgG
measured; 11,364 were followed up after negative
antibody results and 1265 after positive
results, including 88 in whom seroconversion
occurred during follow-up... a total of 223
anti-spike–seronegative health care workers had
a positive PCR test (1.09 per 10,000 days at
risk), 100 during screening while they were
asymptomatic and 123 while symptomatic, whereas
2 anti-spike–seropositive health care workers
had a positive PCR test... the presence of
anti-spike or anti-nucleocapsid IgG antibodies
was associated with a substantially reduced risk
of SARS-CoV-2 reinfection in the ensuing 6
months." |
31)
Researchers find long-lived immunity to 1918
pandemic virus, CIDRAP, 2008
and the actual
2008 NATURE journal publication by Yu |
"A study of the
blood of older people who survived the 1918
influenza pandemic reveals that antibodies to
the strain have lasted a lifetime and can
perhaps be engineered to protect future
generations against similar strains... the group
collected blood samples from 32 pandemic
survivors aged 91 to 101..the people recruited
for the study were 2 to 12 years old in 1918 and
many recalled sick family members in their
households, which suggests they were directly
exposed to the virus, the authors report. The
group found that 100% of the subjects had
serum-neutralizing activity against the 1918
virus and 94% showed serologic reactivity to the
1918 hemagglutinin. The investigators generated
B lymphoblastic cell lines from the peripheral
blood mononuclear cells of eight subjects.
Transformed cells from the blood of 7 of the 8
donors yielded secreting antibodies that bound
the 1918 hemagglutinin." Yu: "here we show that
of the 32 individuals tested that were born in
or before 1915, each showed sero-reactivity with
the 1918 virus, nearly 90 years after the
pandemic. Seven of the eight donor samples
tested had circulating B cells that secreted
antibodies that bound the 1918 HA. We isolated B
cells from subjects and generated five
monoclonal antibodies that showed potent
neutralizing activity against 1918 virus from
three separate donors. These antibodies also
cross-reacted with the genetically similar HA of
a 1930 swine H1N1 influenza strain." |
|
32)
Live virus neutralisation testing in
convalescent patients and subjects vaccinated
against 19A, 20B, 20I/501Y.V1 and 20H/501Y.V2
isolates of SARS-CoV-2, Gonzalez, 2021 |
"No significant
difference was observed between the 20B and 19A
isolates for HCWs with mild COVID-19 and
critical patients. However, a significant
decrease in neutralisation ability was found for
20I/501Y.V1 in comparison with 19A isolate for
critical patients and HCWs 6-months post
infection. Concerning 20H/501Y.V2, all
populations had a significant reduction in
neutralising antibody titres in comparison with
the 19A isolate. Interestingly, a significant
difference in neutralisation capacity was
observed for vaccinated HCWs between the two
variants whereas it was not significant for the
convalescent groups... the reduced neutralising
response observed towards the 20H/501Y.V2 in
comparison with the 19A and 20I/501Y.V1 isolates
in fully immunized subjects with the BNT162b2
vaccine is a striking finding of the study." |
|
33)
Differential effects of the second SARS-CoV-2
mRNA vaccine dose on T cell immunity in naïve
and COVID-19 recovered individuals, Camara,
2021 |
"Characterized
SARS-CoV-2 spike-specific humoral and cellular
immunity in naïve and previously infected
individuals during full BNT162b2 vaccination...
results demonstrate that the second dose
increases both the humoral and cellular immunity
in naïve individuals. On the contrary, the
second BNT162b2 vaccine dose results in a
reduction of cellular immunity in COVID-19
recovered individuals." |
|
34)
Op-Ed: Quit Ignoring Natural COVID Immunity,
Klausner, 2021 |
"Epidemiologists
estimate over 160
million people worldwide have recovered from
COVID-19. Those who have recovered have an
astonishingly low frequency of repeat infection,
disease, or death." |
|
35)
Association of SARS-CoV-2 Seropositive Antibody
Test With Risk of Future Infection, Harvey,
2021 |
"To evaluate
evidence of SARS-CoV-2 infection based on
diagnostic nucleic acid amplification test
(NAAT) among patients with positive vs negative
test results for antibodies in an observational
descriptive cohort study of clinical laboratory
and linked claims data... the cohort included
3 257 478 unique patients with an index antibody
test... patients with positive antibody test
results were initially more likely to have
positive NAAT results, consistent with prolonged
RNA shedding, but became markedly less likely to
have positive NAAT results over time, suggesting
that seropositivity is associated with
protection from infection." |
|
36)
SARS-CoV-2 seropositivity and subsequent
infection risk in healthy young adults: a
prospective cohort study, Letizia, 2021 |
"Investigated the
risk of subsequent SARS-CoV-2 infection among
young adults (CHARM marine study) seropositive
for a previous infection... enrolled 3249
participants, of whom 3168 (98%) continued into
the 2-week quarantine period. 3076 (95%)
participants... Among 189 seropositive
participants, 19 (10%) had at least one positive
PCR test for SARS-CoV-2 during the 6-week
follow-up (1·1 cases per person-year). In
contrast, 1079 (48%) of 2247 seronegative
participants tested positive (6·2 cases per
person-year). The incidence rate ratio was 0·18
(95% CI 0·11–0·28; p<0·001)... infected
seropositive participants had viral loads that
were about 10-times lower than those of infected
seronegative participants (ORF1ab gene cycle
threshold difference 3·95 [95% CI 1·23–6·67];
p=0·004)." |
|
37)
Associations of Vaccination and of Prior
Infection With Positive PCR Test Results for
SARS-CoV-2 in Airline Passengers Arriving in
Qatar, Bertollini, 2021 |
"Of 9,180
individuals with no record of vaccination but
with a record of prior infection at least 90
days before the PCR test (group 3), 7694 could
be matched to individuals with no record of
vaccination or prior infection (group 2), among
whom PCR positivity was 1.01% (95% CI,
0.80%-1.26%) and 3.81% (95% CI, 3.39%-4.26%),
respectively. The relative risk for PCR
positivity was 0.22 (95% CI, 0.17-0.28) for
vaccinated individuals and 0.26 (95% CI,
0.21-0.34) for individuals with prior infection
compared with no record of vaccination or prior
infection." |
|
38)
Natural immunity against COVID-19 significantly
reduces the risk of reinfection: findings from a
cohort of sero-survey participants, Mishra,
2021 |
"Followed up with
a subsample of our previous sero-survey
participants to assess whether natural immunity
against SARS-CoV-2 was associated with a reduced
risk of re-infection (India)... out of the 2238
participants, 1170 were sero-positive and 1068
were sero-negative for antibody against
COVID-19. Our survey found that only 3
individuals in the sero-positive group got
infected with COVID-19 whereas 127 individuals
reported contracting the infection the
sero-negative group... from the 3 sero-positives
re-infected with COVID-19, one had
hospitalization, but did not require oxygen
support or critical care... development of
antibody following natural infection not only
protects against re-infection by the virus to a
great extent, but also safeguards against
progression to severe COVID-19 disease." |
|
39)
Lasting immunity found after recovery from
COVID-19, NIH, 2021 |
"The researchers
found durable immune responses in the majority
of people studied. Antibodies against the spike
protein of SARS-CoV-2, which the virus uses to
get inside cells, were found in 98% of
participants one month after symptom onset. As
seen in previous studies, the number of
antibodies ranged widely between individuals.
But, promisingly, their levels remained fairly
stable over time, declining only modestly at 6
to 8 months after infection... virus-specific B
cells increased over time. People had more
memory B cells six months after symptom onset
than at one month afterwards... levels of T cells
for the virus also remained high after
infection. Six months after symptom onset, 92%
of participants had CD4+ T cells that recognized
the virus... 95% of the people had at least 3 out
of 5 immune-system components that could
recognize SARS-CoV-2 up to 8 months after
infection." |
|
40)
SARS-CoV-2 Natural Antibody Response Persists
for at Least 12 Months in a Nationwide Study
From the Faroe Islands, Petersen, 2021 |
"The seropositive
rate in the convalescent individuals was above
95% at all sampling time points for both assays
and remained stable over time; that is, almost
all convalescent individuals developed
antibodies... results show that SARS-CoV-2
antibodies persisted at least 12 months after
symptom onset and maybe even longer, indicating
that COVID-19-convalescent individuals may be
protected from reinfection." |
|
41)
SARS-CoV-2-specific T cell memory is sustained
in COVID-19 convalescent patients for 10 months
with successful development of stem cell-like
memory T cells, Jung, 2021 |
"ex vivo assays to
evaluate SARS-CoV-2-specific CD4+ and
CD8+ T cell responses in COVID-19
convalescent patients up to 317 days
post-symptom onset (DPSO), and find that memory
T cell responses are maintained during the study
period regardless of the severity of COVID-19.
In particular, we observe sustained
polyfunctionality and proliferation capacity of
SARS-CoV-2-specific T cells. Among
SARS-CoV-2-specific CD4+ and CD8+ T
cells detected by activation-induced markers,
the proportion of stem cell-like memory T (TSCM)
cells is increased, peaking at approximately 120
DPSO." |
|
42)
Immune Memory in Mild COVID-19 Patients and
Unexposed Donors Reveals Persistent T Cell
Responses After SARS-CoV-2 Infection,
Ansari, 2021 |
"Analyzed 42
unexposed healthy donors and 28 mild COVID-19
subjects up to 5 months from the recovery for
SARS-CoV-2 specific immunological memory. Using
HLA class II predicted peptide megapools, we
identified SARS-CoV-2 cross-reactive CD4+ T
cells in around 66% of the unexposed
individuals. Moreover, we found detectable
immune memory in mild COVID-19 patients several
months after recovery in the crucial arms of
protective adaptive immunity; CD4+ T
cells and B cells, with a minimal contribution
from CD8+ T cells. Interestingly, the
persistent immune memory in COVID-19 patients is
predominantly targeted towards the Spike
glycoprotein of the SARS-CoV-2. This study
provides the evidence of both high magnitude
pre-existing and persistent immune memory in
Indian population." |
|
43)
COVID-19 natural immunity, WHO, 2021 |
"Current evidence
points to most individuals developing strong
protective immune responses following natural
infection with SARSCoV-2. Within 4 weeks
following infection, 90-99% of individuals
infected with the SARS-CoV-2 virus develop
detectable neutralizing antibodies. The strength
and duration of the immune responses to
SARS-CoV-2 are not completely understood and
currently available data suggests that it varies
by age and the severity of symptoms. Available
scientific data suggests that in most people
immune responses remain robust and protective
against reinfection for at least 6-8 months
after infection (the longest follow up with
strong scientific evidence is currently
approximately 8 months)." |
|
44)
Antibody Evolution after SARS-CoV-2 mRNA
Vaccination, Cho, 2021 |
"We conclude that
memory antibodies selected over time by natural
infection have greater potency and breadth than
antibodies elicited by vaccination... boosting
vaccinated individuals with currently available
mRNA vaccines would produce a quantitative
increase in plasma neutralizing activity but not
the qualitative advantage against variants
obtained by vaccinating convalescent
individuals." |
|
45)
Humoral Immune Response to SARS-CoV-2 in Iceland,
Gudbjartsson, 2020 |
"Measured
antibodies in serum samples from 30,576 persons
in Iceland... of the 1797 persons who had
recovered from SARS-CoV-2 infection, 1107 of the
1215 who were tested (91.1%) were
seropositive... results indicate risk of death
from infection was 0.3% and that antiviral
antibodies against SARS-CoV-2 did not decline
within 4 months after diagnosis (para)." |
|
46)
Immunological memory to SARS-CoV-2 assessed for
up to 8 months after infection, Dan, 2021 |
"Analyzed multiple
compartments of circulating immune memory to
SARS-CoV-2 in 254 samples from 188 COVID-19
cases, including 43 samples at ≥ 6 months
post-infection... IgG to the Spike protein was
relatively stable over 6+ months. Spike-specific
memory B cells were more abundant at 6 months
than at 1 month post symptom onset." |
|
47)
The prevalence of adaptive immunity to COVID-19
and reinfection after recovery – a comprehensive
systematic review and meta-analysis of 12 011
447 individuals, Chivese, 2021 |
"Fifty-four
studies, from 18 countries, with a total of 12
011 447 individuals, followed up to 8 months
after recovery, were included. At 6-8 months
after recovery, the prevalence of detectable
SARS-CoV-2 specific immunological memory
remained high; IgG – 90.4%... pooled prevalence of
reinfection was 0.2% (95%CI 0.0 – 0.7, I2 =
98.8, 9 studies). Individuals who recovered from
COVID-19 had an 81% reduction in odds of a
reinfection (OR 0.19, 95% CI 0.1 – 0.3, I2 =
90.5%, 5 studies)." |
|
48)
Reinfection Rates among Patients who Previously
Tested Positive for COVID-19: a Retrospective
Cohort Study, Sheehan, 2021 |
"Retrospective
cohort study of one multi-hospital health system
included 150,325 patients tested for COVID-19
infection... prior infection in patients with
COVID-19 was highly protective against
reinfection and symptomatic disease. This
protection increased over time, suggesting that
viral shedding or ongoing immune response may
persist beyond 90 days and may not represent
true reinfection." |
|
49)
Assessment of SARS-CoV-2 Reinfection 1 Year
After Primary Infection in a Population in
Lombardy, Italy, Vitale, 2020 |
"The study results
suggest that reinfections are rare events and
patients who have recovered from COVID-19 have a
lower risk of reinfection. Natural immunity to
SARS-CoV-2 appears to confer a protective effect
for at least a year, which is similar to the
protection reported in recent vaccine studies." |
|
50)
Prior SARS-CoV-2 infection is associated with
protection against symptomatic reinfection,
Hanrath, 2021 |
"We observed no
symptomatic reinfections in a cohort of
healthcare workers... this apparent immunity to
re-infection was maintained for at least 6
months... test positivity rates were 0% (0/128 [95%
CI: 0–2.9]) in those with previous infection
compared to 13.7% (290/2115 [95% CI: 12.3–15.2])
in those without (P<0.0001 χ2 test)." |
|
51)
mRNA vaccine-induced T cells respond identically
to SARS-CoV-2 variants of concern but differ in
longevity and homing properties depending on
prior infection status, Neidleman, 2021 |
"In
infection-naïve individuals, the second dose
boosted the quantity and altered the phenotypic
properties of SARS-CoV-2-specific T cells, while
in convalescents the second dose changed
neither. Spike-specific T cells from
convalescent vaccinees differed strikingly from
those of infection-naïve vaccinees, with
phenotypic features suggesting superior
long-term persistence and ability to home to the
respiratory tract including the nasopharynx." |
|
52)
Targets of T Cell Responses to SARS-CoV-2
Coronavirus in Humans with COVID-19 Disease and
Unexposed Individuals, Grifoni, 2020 |
"Using HLA class I
and II predicted peptide "megapools,"
circulating SARS-CoV-2-specific CD8+ and
CD4+ T cells were identified in ∼70%
and 100% of COVID-19 convalescent patients,
respectively. CD4+ T cell responses
to spike, the main target of most vaccine
efforts, were robust and correlated with the
magnitude of the anti-SARS-CoV-2 IgG and IgA
titers. The M, spike, and N proteins each
accounted for 11%–27% of the total CD4+ response,
with additional responses commonly targeting
nsp3, nsp4, ORF3a, and ORF8, among others. For
CD8+ T cells, spike and M were
recognized, with at least eight SARS-CoV-2 ORFs
targeted." |
|
53)
NIH Director's Blog: Immune T Cells May Offer
Lasting Protection Against COVID-19,
Collins, 2021 |
"Much of the study
on the immune response to SARS-CoV-2, the novel coronavirus that causes COVID-19, has focused on
the production of antibodies.
But, in fact, immune cells known as memory T
cells also play an important role in the ability
of our immune systems to protect us against many
viral infections, including - it now
appears - COVID-19.An intriguing new study of
these memory T cells suggests they might protect
some people newly infected with SARS-CoV-2 by
remembering past encounters with other human
coronaviruses. This might potentially
explain why some people seem to fend off the
virus and may be less susceptible to becoming
severely ill with COVID-19." |
|
54)
Ultrapotent antibodies against diverse and
highly transmissible SARS-CoV-2 variants,
Wang, 2021 |
"Our study
demonstrates that convalescent subjects
previously infected with ancestral variant
SARS-CoV-2 produce antibodies that
cross-neutralize emerging VOCs with high
potency... potent against 23 variants, including
variants of concern." |
|
55)
Why COVID-19 Vaccines Should Not Be Required for
All Americans, Makary, 2021 |
"Requiring the
vaccine in people who are already immune with
natural immunity has no scientific support.
While vaccinating those people may be beneficial
– and it's a reasonable hypothesis that
vaccination may bolster the longevity of their
immunity – to argue dogmatically that they must get
vaccinated has zero clinical outcome data to
back it. As a matter of fact, we have data to
the contrary: A Cleveland Clinic study found
that vaccinating people with natural immunity
did not add to their level of protection." |
|
56)
Protracted yet coordinated differentiation of
long-lived SARS-CoV-2-specific CD8+ T cells
during COVID-19 convalescence, Ma, 2021 |
"Screened 21
well-characterized, longitudinally-sampled
convalescent donors that recovered from mild
COVID-19... following a typical case of mild
COVID-19, SARS-CoV-2-specific CD8+ T cells not
only persist but continuously differentiate in a
coordinated fashion well into convalescence,
into a state characteristic of long-lived,
self-renewing memory." |
|
57)
Decrease in Measles Virus-Specific CD4 T Cell
Memory in Vaccinated Subjects, Naniche, 2004 |
"Characterized the
profiles of measles vaccine (MV) vaccine-induced
antigen-specific T cells over time since
vaccination. In a cross-sectional study of
healthy subjects with a history of MV
vaccination, we found that MV-specific CD4 and
CD8 T cells could be detected up to 34 years
after vaccination. The levels of MV-specific CD8
T cells and MV-specific IgG remained stable,
whereas the level of MV-specific CD4 T cells
decreased significantly in subjects who had been
vaccinated >21 years earlier." |
|
58)
Remembrance of Things Past: Long-Term B Cell
Memory After Infection and Vaccination,
Palm, 2019 |
"The success of
vaccines is dependent on the generation and
maintenance of immunological memory. The immune
system can remember previously encountered
pathogens, and memory B and T cells are critical
in secondary responses to infection. Studies in
mice have helped to understand how different
memory B cell populations are generated
following antigen exposure and how affinity for
the antigen is determinant to B cell fate... upon
re-exposure to an antigen the memory recall
response will be faster, stronger, and more
specific than a naïve response. Protective
memory depends first on circulating antibodies
secreted by LLPCs. When these are not sufficient
for immediate pathogen neutralization and
elimination, memory B cells are recalled." |
|
59)
SARS-CoV-2 specific memory B-cells from
individuals with diverse disease severities
recognize SARS-CoV-2 variants of concern,
Lyski, 2021 |
"Examined the
magnitude, breadth, and durability of SARS-CoV-2
specific antibodies in two distinct B-cell
compartments: long-lived plasma cell-derived
antibodies in the plasma, and peripheral memory
B-cells along with their associated antibody
profiles elicited after in vitro stimulation.
We found that magnitude varied amongst
individuals, but was the highest in hospitalized
subjects. Variants of concern (VoC) -RBD-reactive
antibodies were found in the plasma of 72% of
samples in this investigation, and
VoC-RBD-reactive memory B-cells were found in
all but 1 subject at a single time-point. This
finding, that VoC-RBD-reactive MBCs are present
in the peripheral blood of all subjects
including those that experienced asymptomatic or
mild disease, provides a reason for optimism
regarding the capacity of vaccination, prior
infection, and/or both, to limit disease
severity and transmission of variants of concern
as they continue to arise and circulate." |
|
60)
Exposure to SARS-CoV-2 generates T-cell memory
in the absence of a detectable viral infection,
Wang, 2021 |
"T-cell immunity
is important for recovery from COVID-19 and
provides heightened immunity for re-infection.
However, little is known about the
SARS-CoV-2-specific T-cell immunity in
virus-exposed individuals... report virus-specific
CD4+ and CD8+ T-cell
memory in recovered COVID-19 patients and close
contacts... close contacts are able to gain T-cell
immunity against SARS-CoV-2 despite lacking a
detectable infection." |
|
61)
CD8+ T-Cell Responses in COVID-19 Convalescent
Individuals Target Conserved Epitopes From
Multiple Prominent SARS-CoV-2 Circulating
Variants, Redd, 2021and
Lee, 2021 |
"The CD4 and CD8
responses generated after natural infection are
equally robust, showing activity against
multiple "epitopes" (little segments) of the
spike protein of the virus. For instance, CD8
cells responds to 52
epitopes and CD4 cells respond to 57
epitopes across the spike protein, so that a
few mutations in the variants cannot knock out
such a robust and in-breadth T cell response...
only 1 mutation found in Beta variant-spike
overlapped with a previously identified epitope
(1/52), suggesting that virtually all
anti-SARS-CoV-2 CD8+ T-cell responses should
recognize these newly described variants." |
|
62)
Exposure to common cold coronaviruses can teach
the immune system to recognize SARS-CoV-2,La
Jolla, Crotty and Sette, 2020 |
"Exposure to
common cold coronaviruses can teach the immune
system to recognize SARS-CoV-2" |
|
63)
Selective and cross-reactive SARS-CoV-2 T cell
epitopes in unexposed humans, Mateus, 2020 |
"Found that the
pre-existing reactivity against SARS-CoV-2 comes
from memory T cells and that cross-reactive T
cells can specifically recognize a SARS-CoV-2 epitope as well as the homologous epitope from a
common cold coronavirus. These findings
underline the importance of determining the
impacts of pre-existing immune memory in
COVID-19 disease severity." |
|
64)
Longitudinal observation of antibody responses
for 14 months after SARS-CoV-2 infection,
Dehgani-Mobaraki, 2021 |
"Better
understanding of antibody
responses against SARS-CoV-2 after natural
infection might provide valuable insights into
the future implementation of vaccination
policies. Longitudinal analysis of IgG antibody
titers was carried out in 32 recovered
COVID-19 patients based in the Umbria region
of Italy for 14 months after Mild and
Moderately-Severe infection... study findings are
consistent with recent studies reporting
antibody persistency suggesting that induced
SARS-CoV-2 immunity through natural infection,
might be very efficacious against re-infection
(>90%) and could persist for more than six
months. Our study followed up patients up to
14 months demonstrating the presence of
anti-S-RBD IgG in 96.8% of recovered COVID-19
subjects." |
|
65)
Humoral and circulating follicular helper T cell
responses in recovered patients with COVID-19,
Juno, 2020 |
"Characterized
humoral and circulating follicular helper T cell
(cTFH) immunity against spike in recovered
patients with coronavirus disease 2019
(COVID-19). We found that S-specific antibodies,
memory B cells and cTFH are consistently
elicited after SARS-CoV-2 infection, demarking
robust humoral immunity and positively
associated with plasma neutralizing activity." |
|
66)
Convergent antibody responses to SARS-CoV-2 in
convalescent individuals, Robbiani, 2020 |
"149
COVID-19-convalescent individuals... antibody
sequencing revealed the expansion of clones of
RBD-specific memory B cells that expressed
closely related antibodies in different
individuals. Despite low plasma titres,
antibodies to three distinct epitopes on the RBD
neutralized the virus with half-maximal
inhibitory concentrations (IC50 values)
as low as 2 ng ml−1." |
|
67)
Rapid generation of durable B cell memory to
SARS-CoV-2 spike and nucleocapsid proteins in
COVID-19 and convalescence, Hartley, 2020 |
"COVID-19 patients
rapidly generate B cell memory to both the spike
and nucleocapsid antigens following SARS-CoV-2
infection... RBD- and NCP-specific IgG and Bmem
cells were detected in all 25 patients with a
history of COVID-19." |
|
68)
Had COVID? You'll probably make antibodies for a
lifetime, Callaway, 2021 |
"People who
recover from mild COVID-19 have bone-marrow
cells that can churn out antibodies for
decades... the study provides evidence that
immunity triggered by SARS-CoV-2 infection will
be extraordinarily long-lasting." |
|
69)
A majority of uninfected adults show preexisting
antibody reactivity against SARS-CoV-2,
Majdoubi, 2021 |
In greater
Vancouver Canada, "using a highly sensitive
multiplex assay and positive/negative thresholds
established in infants in whom maternal
antibodies have waned, we determined that more
than 90% of uninfected adults showed antibody
reactivity against the spike protein,
receptor-binding domain (RBD), N-terminal domain
(NTD), or the nucleocapsid (N) protein from
SARS-CoV-2." |
|
70)
SARS-CoV-2-reactive T cells in healthy donors
and patients with COVID-19, Braun, 2020 |
"The results
indicate that spike-protein cross-reactive T
cells are present, which were probably generated
during previous encounters with endemic
coronaviruses." |
|
71)
Naturally enhanced neutralizing breadth against
SARS-CoV-2 one year after infection, Wang,
2021 |
"A cohort of 63
individuals who have recovered from COVID-19
assessed at 1.3, 6.2 and 12 months after
SARS-CoV-2 infection... the data suggest that
immunity in convalescent individuals will be
very long lasting." |
|
72)
One Year after Mild COVID-19: The Majority of
Patients Maintain Specific Immunity, But One in
Four Still Suffer from Long-Term Symptoms,
Rank, 2021 |
"Long-lasting
immunological memory against SARS-CoV-2 after
mild COVID-19." |
|
73)
IDSA, 2021 |
"Immune responses
to SARS-CoV-2 following natural infection can
persist for at least 11 months... natural
infection (as determined by a prior positive
antibody or PCR-test result) can confer
protection against SARS-CoV-2 infection." |
|
74)
Assessment of protection against reinfection
with SARS-CoV-2 among 4 million PCR-tested
individuals in Denmark in 2020: a
population-level observational study, Holm
Hansen, 2021 |
Denmark, "during
the first surge (ie, before June, 2020), 533 381
people were tested, of whom 11 727 (2·20%) were
PCR positive, and 525 339 were eligible for
follow-up in the second surge, of whom 11 068
(2·11%) had tested positive during the first
surge. Among eligible PCR-positive individuals
from the first surge of the epidemic, 72 (0·65%
[95% CI 0·51–0·82]) tested positive again during
the second surge compared with 16 819 (3·27%
[3·22–3·32]) of 514 271 who tested negative
during the first surge (adjusted RR 0·195 [95%
CI 0·155–0·246])." |
|
75)
Antigen-Specific Adaptive Immunity to SARS-CoV-2
in Acute COVID-19 and Associations with Age and
Disease Severity, Moderbacher, 2020 |
"Adaptive immune
responses limit COVID-19 disease
severity... multiple coordinated arms of adaptive
immunity control better than partial
responses... completed a combined examination of
all three branches of adaptive immunity at the
level of SARS-CoV-2-specific CD4+ and
CD8+ T cell and neutralizing antibody
responses in acute and convalescent subjects.
SARS-CoV-2-specific CD4+ and CD8+ T cells
were each associated with milder disease.
Coordinated SARS-CoV-2-specific adaptive immune
responses were associated with milder disease,
suggesting roles for both CD4+ and
CD8+ T cells in protective immunity
in COVID-19." |
|
76)
Detection of SARS-CoV-2-Specific Humoral and
Cellular Immunity in COVID-19 Convalescent
Individuals, Ni, 2020 |
"Collected blood
from COVID-19 patients who have recently become
virus-free, and therefore were discharged, and
detected SARS-CoV-2-specific humoral and
cellular immunity in eight newly discharged
patients. Follow-up analysis on another cohort
of six patients 2 weeks post discharge also
revealed high titers of immunoglobulin G (IgG)
antibodies. In all 14 patients tested, 13
displayed serum-neutralizing activities in a
pseudotype entry assay. Notably, there was a
strong correlation between neutralization
antibody titers and the numbers of
virus-specific T cells." |
|
77)
Robust SARS-CoV-2-specific T-cell immunity is
maintained at 6 months following primary
infection, Zuo, 2020 |
"Analysed the
magnitude and phenotype of the SARS-CoV-2
cellular immune response in 100 donors at six
months following primary infection and related
this to the profile of antibody level against
spike, nucleoprotein and RBD over the previous
six months. T-cell immune responses to
SARS-CoV-2 were present by ELISPOT and/or ICS
analysis in all donors and are characterised by
predominant CD4+ T cell responses with strong
IL-2 cytokine expression... functional
SARS-CoV-2-specific T-cell responses are
retained at six months following infection." |
|
78)
Negligible impact of SARS-CoV-2 variants on CD4+ and
CD8+ T cell reactivity in COVID-19
exposed donors and vaccinees, Tarke, 2021 |
"Performed a
comprehensive analysis of SARS-CoV-2-specific
CD4+ and CD8+ T cell responses from COVID-19
convalescent subjects recognizing the ancestral
strain, compared to variant lineages B.1.1.7,
B.1.351, P.1, and CAL.20C as well as recipients
of the Moderna (mRNA-1273) or Pfizer/BioNTech
(BNT162b2) COVID-19 vaccines... the sequences of
the vast majority of SARS-CoV-2 T cell epitopes
are not affected by the mutations found in the
variants analyzed. Overall, the results
demonstrate that CD4+ and CD8+ T cell responses
in convalescent COVID-19 subjects or COVID-19
mRNA vaccinees are not substantially affected by
mutations." |
|
79)
A 1 to 1000 SARS-CoV-2 reinfection proportion in
members of a large healthcare provider in
Israel: a preliminary report, Perez, 2021 |
Israel, "out of
149,735 individuals with a documented positive
PCR test between March 2020 and January 2021,
154 had two positive PCR tests at least 100 days
apart, reflecting a reinfection proportion of 1
per 1000." |
|
80) Persistence
and decay of human antibody responses to the
receptor binding domain of SARS-CoV-2 spike
protein in COVID-19 patients, Iyer, 2020 |
"Measured plasma
and/or serum antibody responses to the
receptor-binding domain (RBD) of the spike (S)
protein of SARS-CoV-2 in 343 North American
patients infected with SARS-CoV-2 (of which 93%
required hospitalization) up to 122 days after
symptom onset and compared them to responses in
1548 individuals whose blood samples were
obtained prior to the pandemic... IgG antibodies
persisted at detectable levels in patients
beyond 90 days after symptom onset, and
seroreversion was only observed in a small
percentage of individuals. The concentration of
these anti-RBD IgG antibodies was also highly
correlated with pseudovirus NAb titers, which
also demonstrated minimal decay. The observation
that IgG and neutralizing antibody responses
persist is encouraging, and suggests the
development of robust systemic immune memory in
individuals with severe infection." |
|
81) A
population-based analysis of the longevity of
SARS-CoV-2 antibody seropositivity in the United
States, Alfego, 2021 |
"To track
population-based SARS-CoV-2 antibody seropositivity duration across the United States
using observational data from a national
clinical laboratory registry of patients tested
by nucleic acid amplification (NAAT) and
serologic assays... specimens from 39,086
individuals with confirmed positive
COVID-19... both S and N SARS-CoV-2 antibody
results offer an encouraging view of how long
humans may have protective antibodies against
COVID-19, with curve smoothing showing
population seropositivity reaching 90% within
three weeks, regardless of whether the assay
detects N or S-antibodies. Most importantly,
this level of seropositivity was sustained with
little decay through ten months after initial
positive PCR." |
|
82)
What are the roles of antibodies versus a
durable, high- quality T-cell response in
protective immunity against SARS-CoV-2?
Hellerstein, 2020 |
"Progress in
laboratory markers for SARS-CoV2 has been made
with identification of epitopes on CD4 and CD8
T-cells in convalescent blood. These are much
less dominated by spike protein than in previous
coronavirus infections. Although most vaccine
candidates are focusing on spike protein as
antigen, natural infection by SARS-CoV-2 induces
broad epitope coverage, cross-reactive with
other betacoronviruses." |
|
83)
Broad and strong memory CD4+ and CD8+ T
cells induced by SARS-CoV-2 in UK convalescent
COVID-19 patients, Peng, 2020 |
"Study of 42
patients following recovery from COVID-19,
including 28 mild and 14 severe cases, comparing
their T cell responses to those of 16 control
donors... found the breadth, magnitude and
frequency of memory T cell responses from
COVID-19 were significantly higher in severe
compared to mild COVID-19 cases, and this effect
was most marked in response to spike, membrane,
and ORF3a proteins... total and spike-specific T
cell responses correlated with the anti-Spike,
anti-Receptor Binding Domain (RBD) as well as
anti-Nucleoprotein (NP) endpoint antibody
titre... furthermore showed a higher ratio of
SARS-CoV-2-specific
CD8+ to CD4+ T cell
responses... immunodominant epitope clusters and
peptides containing T cell epitopes identified
in this study will provide critical tools to
study the role of virus-specific T cells in
control and resolution of SARS-CoV-2
infections." |
|
84)
Robust T Cell Immunity in Convalescent
Individuals with Asymptomatic or Mild COVID-19,
Sekine, 2020 |
"SARS-CoV-2-specific memory T cells will likely
prove critical for long-term immune protection
against COVID-19... mapped the functional and
phenotypic landscape of SARS-CoV-2-specific T
cell responses in unexposed individuals, exposed
family members, and individuals with acute or
convalescent COVID-19... collective dataset
shows that SARS-CoV-2 elicits broadly directed
and functionally replete memory T cell
responses, suggesting that natural exposure or
infection may prevent recurrent episodes of
severe COVID-19." |
|
85)
Potent SARS-CoV-2-Specific T Cell Immunity and
Low Anaphylatoxin Levels Correlate With Mild
Disease Progression in COVID-19 Patients,
Lafron, 2021 |
"Provide a full
picture of cellular and humoral immune responses
of COVID-19 patients and prove that robust
polyfunctional CD8+ T cell responses
concomitant with low anaphylatoxin levels
correlate with mild infections." |
|
86)
SARS-CoV-2 T-cell epitopes define heterologous
and COVID-19 induced T-cell recognition,
Nelde, 2020 |
"The first work
identifying and characterizing
SARS-CoV-2-specific and cross-reactive HLA class
I and HLA-DR T-cell epitopes in SARS-CoV-2
convalescents (n = 180) as well as unexposed
individuals (n = 185) and confirming their
relevance for immunity and COVID-19 disease
course... cross-reactive SARS-CoV-2 T-cell epitopes
revealed pre-existing T-cell responses in 81% of
unexposed individuals, and validation of
similarity to common cold human coronaviruses
provided a functional basis for postulated
heterologous immunity in SARS-CoV-2
infection... intensity of T-cell responses and
recognition rate of T-cell epitopes was
significantly higher in the convalescent donors
compared to unexposed individuals, suggesting
that not only expansion, but also diversity
spread of SARS-CoV-2 T-cell responses occur upon
active infection." |
|
87)
Karl Friston: up to 80% not even susceptible to
Covid-19, Sayers, 2020 |
"Results have just
been published of
a study suggesting that 40%-60% of people who
have not been exposed to coronavirus have
resistance at the T-cell level from other
similar coronaviruses like the common cold...
the true portion of people who are not even
susceptible to Covid-19 may be as high as 80%." |
|
88)
CD8+ T cells specific for an
immunodominant SARS-CoV-2 nucleocapsid epitope
cross-react with selective seasonal
coronaviruses, Lineburg, 2021 |
"Screening of
SARS-CoV-2 peptide pools revealed that the nucleocapsid (N) protein induced an
immunodominant response in HLA-B7+ COVID-19-recovered
individuals that was also detectable in
unexposed donors... the basis of selective T cell
cross-reactivity for an immunodominant
SARS-CoV-2 epitope and its homologs from
seasonal coronaviruses, suggesting long-lasting
protective immunity." |
|
89)
SARS-CoV-2 genome-wide mapping of CD8 T cell
recognition reveals strong immunodominance and
substantial CD8 T cell activation in COVID-19
patients, Saini, 2020 |
"COVID-19 patients
showed strong T cell responses, with up to 25%
of all CD8+ lymphocytes specific to
SARS-CoV-2-derived immunodominant epitopes,
derived from ORF1 (open reading frame 1), ORF3,
and Nucleocapsid (N) protein. A strong signature
of T cell activation was observed in COVID-19
patients, while no T cell activation was seen in
the 'non-exposed' and 'high exposure risk'
healthy donors." |
|
90)
Equivalency of Protection from Natural Immunity
in COVID-19 Recovered Versus Fully Vaccinated
Persons: A Systematic Review and Pooled Analysis,
Shenai, 2021 |
"Systematic review
and pooled analysis of clinical studies to date,
that (1) specifically compare the protection of
natural immunity in the COVID-recovered versus
the efficacy of full vaccination in the
COVID-naive, and (2) the added benefit of
vaccination in the COVID-recovered, for
prevention of subsequent SARS-CoV-2
infection... review demonstrates that natural
immunity in COVID-recovered individuals is, at
least, equivalent to the protection afforded by
full vaccination of COVID-naïve populations.
There is a modest and incremental relative
benefit to vaccination in COVID-recovered
individuals; however, the net benefit is
marginal on an absolute basis." |
|
91)
ChAdOx1nCoV-19 effectiveness during an
unprecedented surge in SARS CoV-2 infections,
Satwik, 2021 |
"The third key
finding is that previous infections with
SARS-CoV-2 were significantly protective against
all studied outcomes, with an effectiveness of
93% (87 to 96%) seen against symptomatic
infections, 89% (57 to 97%) against moderate to
severe disease and 85% (-9 to 98%) against
supplemental oxygen therapy. All deaths occurred
in previously uninfected individuals. This was
higher protection than that offered by single or
double dose vaccine." |
92) SARS-CoV-2
specific T cells and antibodies in COVID-19
protection: a prospective study,
Molodtsov, 2021 |
"Explore the
impact of T cells and to quantify the protective
levels of the immune responses... 5,340 Moscow
residents were evaluated for the antibody and
cellular immune responses to SARS-CoV-2 and
monitored for COVID-19 up to 300 days. The
antibody and cellular responses were tightly
interconnected, their magnitude inversely
correlated with infection probability. Similar
maximal level of protection was reached by
individuals positive for both types of responses
and by individuals with antibodies alone... T
cells in the absence of antibodies provided an
intermediate level of protection." |
|
93) Negligible
impact of SARS-CoV-2 variants on CD4+ and
CD8+ T cell reactivity in COVID-19
exposed donors and vaccinees, Tarke, 2021 |
"Demonstrate that
the sequences of the vast majority of SARS-CoV-2
T cell epitopes are not affected by the
mutations found in the variants analyzed.
Overall, the results demonstrate that CD4+ and
CD8+ T cell responses in convalescent COVID-19
subjects or COVID-19 mRNA vaccinees are not
substantially affected by mutations found in the
SARS-CoV-2 variants." |
|
94) Anti-
SARS-CoV-2 Receptor Binding Domain Antibody
Evolution after mRNA Vaccination, Cho, 2021 |
"SARS-CoV-2
infection produces B-cell responses that
continue to evolve for at least one year. During
that time, memory B cells express increasingly
broad and potent antibodies that are resistant
to mutations found in variants of concern." |
|
95) Seven-month
kinetics of SARS-CoV-2 antibodies and role of
pre-existing antibodies to human coronaviruses,
Ortega, 2021 |
"Impact of pre-existing antibodies to human coronaviruses causing common cold (HCoVs), is
essential to understand protective immunity to
COVID-19 and devise effective surveillance
strategies... after the peak response, anti-spike
antibody levels increase from ~150 days
post-symptom onset in all individuals (73% for IgG), in the absence of any evidence of
re-exposure. IgG and IgA to HCoV are
significantly higher in asymptomatic than
symptomatic seropositive individuals. Thus,
pre-existing cross-reactive HCoVs antibodies
could have a protective effect against
SARS-CoV-2 infection and COVID-19 disease." |
|
96) Immunodominant
T-cell epitopes from the SARS-CoV-2 spike
antigen reveal robust pre-existing T-cell
immunity in unexposed individuals, Mahajan,
2021 |
"Findings suggest
that SARS-CoV-2 reactive T-cells are likely to
be present in many individuals because of prior
exposure to flu and CMV viruses." |
|
97) Detection
of SARS-CoV-2-Specific Humoral and Cellular
Immunity in COVID-19 Convalescent Individuals,
Ni, 2020 |
"Collected blood
from COVID-19 patients who have recently become
virus-free, and therefore were discharged, and
detected SARS-CoV-2-specific humoral and
cellular immunity in eight newly discharged
patients... In all 14 patients tested, 13
displayed serum-neutralizing activities in a pseudotype entry assay. Notably, there was a
strong correlation between neutralization
antibody titers and the numbers of
virus-specific T cells." |
|
98) Neutralizing
Antibody Responses to Severe Acute Respiratory
Syndrome Coronavirus 2 in Coronavirus Disease
2019 Inpatients and Convalescent Patients,
Wang, 2020 |
"117 blood samples were collected from 70
COVID-19 inpatients and convalescent patients...
the neutralizing antibodies were detected even
at the early stage of disease, and a significant
response was shown in convalescent patients."
|
|
99) Not
just antibodies: B cells and T cells mediate
immunity to COVID-19, Cox, 2020 |
"Reports that
antibodies to SARS-CoV-2 are not maintained in
the serum following recovery from the virus have
caused alarm... the absence of specific
antibodies in the serum does not necessarily
mean an absence of immune memory." |
|
100) T
cell immunity to SARS-CoV-2 following natural
infection and vaccination, DiPiazza,
2020 |
"Although T cell
durability to SARS-CoV-2 remains to be
determined, current data and past experience
from human infection with other CoVs demonstrate
the potential for persistence and the capacity
to control viral replication and host disease,
and importance in vaccine-induced protection." |
|
101) Durable
SARS-CoV-2 B cell immunity after mild or severe
disease, Ogega, 2021 |
"Multiple studies
have shown loss of severe acute respiratory
syndrome coronavirus 2-specific
(SARS-CoV-2-specific) antibodies over time after
infection, raising concern that humoral immunity
against the virus is not durable. If immunity
wanes quickly, millions of people may be at risk
for reinfection after recovery from coronavirus
disease 2019 (COVID-19). However, memory B cells
(MBCs) could provide durable humoral immunity
even if serum neutralizing antibody titers
decline... data indicate that most
SARS-CoV-2-infected individuals develop
S-RBD-specific, class-switched rMBCs that
resemble germinal center-derived B cells induced
by effective vaccination against other
pathogens, providing evidence for durable B
cell-mediated immunity against SARS-CoV-2 after
mild or severe disease." |
|
102) Memory
T cell responses targeting the SARS coronavirus
persist up to 11 years post-infection., Ng,
2016 |
"All memory T cell
responses detected target the SARS-Co-V
structural proteins... these responses were
found to persist up to 11 years
post-infection... knowledge of the persistence
of SARS-specific celullar immunity targeting the
viral structural proteins in SARS-recovered
individuals is important." |
|
103) Adaptive
immunity to SARS-CoV-2 and COVID-19, Sette,
2021 |
"The adaptive
immune system is important for control of most
viral infections. The three fundamental
components of the adaptive immune system are B
cells (the source of antibodies), CD4+ T cells,
and CD8+ T cells... a picture has begun to
emerge that reveals that CD4+ T cells, CD8+ T
cells, and neutralizing antibodies all
contribute to control of SARS-CoV-2 in both
non-hospitalized and hospitalized cases of
COVID-19." |
|
104) Early
induction of functional SARS-CoV-2-specific T
cells associates with rapid viral clearance and
mild disease in COVID-19 patients, Tan, 2021 |
"These findings
provide support for the prognostic value of
early functional SARS-CoV-2-specific T cells
with important implications in vaccine design
and immune monitoring." |
|
105) SARS-CoV-2–specific
CD8+ T cell responses in convalescent
COVID-19 individuals, Kared,
2021 |
"A multiplexed
peptide-MHC tetramer approach was used to screen
408 SARS-CoV-2 candidate epitopes for CD8+ T
cell recognition in a cross-sectional sample of
30 coronavirus disease 2019 convalescent
individuals... Modelling demonstrated a coordinated
and dynamic immune response characterized by a
decrease in inflammation, increase in
neutralizing antibody titer, and differentiation
of a specific CD8+ T cell response.
Overall, T cells exhibited distinct
differentiation into stem cell and transitional
memory states (subsets), which may be key to
developing durable protection." |
|
106) S
Protein-Reactive IgG and Memory B Cell
Production after Human SARS-CoV-2 Infection
Includes Broad Reactivity to the S2 Subunit, Nguyen-Contant,
2021 |
"Most importantly,
we demonstrate that infection generates both IgG
and IgG MBCs against the novel receptor binding
domain and the conserved S2 subunit of the
SARS-CoV-2 spike protein. Thus, even if antibody
levels wane, long-lived MBCs remain to mediate
rapid antibody production. Our study results
also suggest that SARS-CoV-2 infection
strengthens pre-existing broad coronavirus
protection through S2-reactive antibody and MBC
formation." |
|
107) Persistence
of Antibody and Cellular Immune Responses in
Coronavirus Disease 2019 Patients Over Nine
Months After Infection, Yao, 2021 |
A cross-sectional
study to assess the virus-specific antibody and
memory T and B cell responses in coronavirus
disease 2019 (COVID-19) patients up to 343 days
after infection... found that approximately 90% of
patients still have detectable immunoglobulin (Ig)G
antibodies against spike and nucleocapsid
proteins and neutralizing antibodies against
pseudovirus, whereas ~60% of patients had
detectable IgG antibodies against
receptor-binding domain and surrogate
virus-neutralizing
antibodies... SARS-CoV-2-specific IgG+ memory B
cell and interferon-γ-secreting T cell responses
were detectable in more than 70% of patients... coronavirus
2-specific immune memory response persists in
most patients approximately 1 year after
infection, which provides a promising sign for
prevention from reinfection and vaccination
strategy." |
|
108) Naturally
Acquired SARS-CoV-2 Immunity Persists for Up to
11 Months Following Infection, De
Giorgi, 2021 |
"A prospective,
longitudinal analysis of COVID-19 convalescent
plasma donors at multiple time points over an
11-month period to determine how circulating
antibody levels change over time following
natural infection... data suggest that
immunological memory is acquired in most
individuals infected with SARS-CoV-2 and is
sustained in a majority of patients." |
|
109) Decreasing
Seroprevalence of Measles Antibodies after
Vaccination – Possible Gap in Measles Protection
in Adults in the Czech Republic, Smetana,
2017 |
"A long-term high
rate of seropositivity persists after natural
measles infection. By contrast, it decreases
over time after vaccination. Similarly, the
concentrations of antibodies in persons with
measles history persist for a longer time at a
higher level than in vaccinated persons." |
|
110) Broadly
cross-reactive antibodies dominate the human B
cell response against 2009 pandemic H1N1
influenza virus infection, Wrammert, 2011 |
"The expansion of
these rare types of memory B cells may explain
why most people did not become severely ill,
even in the absence of pre-existing protective
antibody titers"... found "extraordinarily"
powerful antibodies in the blood of nine people
who caught the swine flu naturally and recovered
from it."... unlike antibodies elicited by
annual influenza vaccinations, most neutralizing
antibodies induced by pandemic H1N1 infection
were broadly cross-reactive against epitopes in
the hemagglutinin (HA) stalk and head domain of
multiple influenza strains. The antibodies were
from cells that had undergone extensive affinity
maturation." |
|
111) Reinfection
With Severe Acute Respiratory Syndrome
Coronavirus 2 (SARS-CoV-2) in Patients
Undergoing Serial Laboratory Testing,
Qureshi, 2021 |
"Reinfection was
identified in 0.7% (n = 63, 95% confidence
interval [CI]: .5%–.9%) during follow-up of 9119
patients with SARS-CoV-2 infection." |
|
112) Distinct
antibody and memory B cell responses in
SARS-CoV-2 naïve and recovered individuals
following mRNA vaccination, Goel, 2021 |
"Interrogated
antibody and antigen-specific memory B cells
over time in 33 SARS-CoV-2 naïve and 11
SARS-CoV-2 recovered subjects... In SARS-CoV-2
recovered individuals, antibody and memory B
cell responses were significantly boosted after
the first vaccine dose; however, there was no
increase in circulating antibodies, neutralizing
titers, or antigen-specific memory B cells after
the second dose. This robust boosting after the
first vaccine dose strongly correlated with
levels of pre-existing memory B cells in
recovered individuals, identifying a key role
for memory B cells in mounting recall responses
to SARS-CoV-2 antigens." |
|
113) Covid-19:
Do many people have pre-existing immunity?Doshi,
2021 |
"Six studies have
reported T cell reactivity against SARS-CoV-2 in
20% to 50% of people with no known exposure to
the virus... in a study of donor blood specimens
obtained in the US between 2015 and 2018, 50%
displayed various forms of T cell reactivity to
SARS-CoV-2... Researchers are also confident that
they have made solid inroads into ascertaining
the origins of the immune responses. "Our
hypothesis, of course, was that it's so called
'common cold' coronaviruses, because they're
closely related... we have really shown that this
is a true immune memory and it is derived in
part from common cold viruses." |
|
114) Pre-existing
and de novo humoral immunity to
SARS-CoV-2 in humans, Ng, 2020 |
"We demonstrate
the presence of pre-existing humoral immunity in
uninfected and unexposed humans to the new
coronavirus. SARS-CoV-2 S-reactive antibodies
were readily detectable by a sensitive flow
cytometry-based method in SARS-CoV-2-uninfected
individuals and were particularly prevalent in
children and adolescents." |
|
115) Phenotype
of SARS-CoV-2-specific T-cells in COVID-19
patients with acute respiratory distress
syndrome, Weiskopf, 2020 |
"We detected
SARS-CoV-2-specific CD4+ and CD8+ T
cells in 100% and 80% of COVID-19 patients,
respectively. We also detected low levels of
SARS-CoV-2-reactive T-cells in 20% of the
healthy controls, not previously exposed to
SARS-CoV-2 and indicative of cross-reactivity
due to infection with 'common cold'
coronaviruses." |
|
116) Pre-existing
immunity to SARS-CoV-2: the knowns and unknowns,
Sette, 2020 |
"T cell reactivity
against SARS-CoV-2 was observed in unexposed
people... it is speculated that this reflects T
cell memory to circulating 'common cold'
coronaviruses." |
|
117) Pre-existing
immunity against swine-origin H1N1 influenza
viruses in the general human population,
Greenbaum, 2009 |
"Memory T-cell
immunity against S-OIV is present in the adult
population and that such memory is of similar
magnitude as the pre-existing memory against
seasonal H1N1 influenza... the conservation of a
large fraction of T-cell epitopes suggests that
the severity of an S-OIV infection, as far as it
is determined by susceptibility of the virus to
immune attack, would not differ much from that
of seasonal flu." |
|
118) Cellular
immune correlates of protection against
symptomatic pandemic influenza, Sridhar,
2013 |
"The 2009 H1N1
pandemic (pH1N1) provided a unique natural
experiment to determine whether cross-reactive
cellular immunity limits symptomatic illness in
antibody-naive individuals... Higher frequencies
of pre-existing T cells to conserved CD8
epitopes were found in individuals who developed
less severe illness, with total symptom score
having the strongest inverse correlation with
the frequency of interferon-γ (IFN-γ)(+)
interleukin-2 (IL-2)(-) CD8(+) T cells (r =
-0.6, P = 0.004)... CD8(+) T cells specific to
conserved viral epitopes correlated with
cross-protection against symptomatic influenza." |
|
119) Preexisting
influenza-specific CD4+ T cells correlate with
disease protection against influenza challenge
in humans, Wilkinson, 2012 |
"Precise role of T
cells in human influenza immunity is uncertain.
We conducted influenza infection studies in
healthy volunteers with no detectable antibodies
to the challenge viruses H3N2 or H1N1... mapped
T cell responses to influenza before and during
infection... found a large increase in
influenza-specific T cell responses by day 7,
when virus was completely cleared from nasal
samples and serum antibodies were still
undetectable. Pre-existing CD4+, but not CD8+, T
cells responding to influenza internal proteins
were associated with lower virus shedding and
less severe illness. These CD4+ cells also
responded to pandemic H1N1 (A/CA/07/2009)
peptides and showed evidence of cytotoxic
activity." |
|
120) Serum
cross-reactive antibody response to a novel
influenza A (H1N1) virus after vaccination with
seasonal influenza vaccine, CDC, MMWR, 2009 |
"No increase in
cross-reactive antibody response to the novel
influenza A (H1N1) virus was observed among
adults aged >60 years. These data suggest that
receipt of recent (2005–2009) seasonal influenza
vaccines is unlikely to elicit a protective
antibody response to the novel influenza A
(H1N1) virus." |
|
121) No
one is naive: the significance of heterologous
T-cell immunity, Welsh, 2002 |
"Memory T cells
that are specific for one virus can become
activated during infection with an unrelated heterologous virus, and might have roles in
protective immunity and immunopathology. The
course of each infection is influenced by the
T-cell memory pool that has been laid down by a
host's history of previous infections, and with
each successive infection, T-cell memory to
previously encountered agents is modified." |
|
122) Intrafamilial
Exposure to SARS-CoV-2 Induces Cellular Immune
Response without Seroconversion, Gallais,
2020 |
"Individuals
belonging to households with an index COVID-19
patient, reported symptoms of COVID-19 but
discrepant serology results... All index patients
recovered from a mild COVID-19. They all
developed anti-SARS-CoV-2 antibodies and a
significant T cell response detectable up to 69
days after symptom onset. Six of the eight
contacts reported COVID-19 symptoms within 1 to
7 days after the index patients but all were
SARS-CoV-2 seronegative... exposure to SARS-CoV-2
can induce virus-specific T cell responses
without seroconversion. T cell responses may be
more sensitive indicators of SARS-Co-V-2
exposure than antibodies... results indicate
that epidemiological data relying only on the
detection of SARS-CoV-2 antibodies may lead to a
substantial underestimation of prior exposure to
the virus." |
|
123) Protective
immunity after recovery from SARS-CoV-2
infection, Kojima, 2021 |
"It important to
note that antibodies are incomplete predictors
of protection. After vaccination or infection,
many mechanisms of immunity exist within an
individual not only at the antibody level, but
also at the level of cellular immunity. It is
known that SARS-CoV-2 infection induces specific
and durable T-cell immunity, which has multiple
SARS-CoV-2 spike protein targets (or epitopes)
as well as other SARS-CoV-2 protein targets. The
broad diversity of T-cell viral recognition
serves to enhance protection to SARS-CoV-2
variants, with recognition of at least the alpha
(B.1.1.7), beta (B.1.351), and gamma (P.1)
variants of SARS-CoV-2. Researchers have also
found that people who recovered from SARS-CoV
infection in 2002–03 continue to have memory T
cells that are reactive to SARS-CoV proteins 17
years after that outbreak. Additionally, a
memory B-cell response to SARS-CoV-2 evolves
between 1·3 and 6·2 months after infection,
which is consistent with longer-term
protection." |
|
124) This
'super antibody' for COVID fights off multiple
coronaviruses, Kwon, 2021 |
"This 'super
antibody' for COVID fights off multiple
coronaviruses... 12 antibodies... that was involved in
the study, isolated from people who had been
infected with either SARS-CoV-2 or its close
relative SARS-CoV." |
|
125) SARS-CoV-2
infection induces sustained humoral immune
responses in convalescent patients following
symptomatic COVID-19, Wu, 2020 |
"Taken together,
our data indicate sustained humoral immunity in
recovered patients who suffer from symptomatic
COVID-19, suggesting prolonged immunity." |
|
126) Evidence
for sustained mucosal and systemic antibody
responses to SARS-CoV-2 antigens in COVID-19
patients, Isho, 2020 |
"Whereas
anti-CoV-2 IgA antibodies rapidly decayed, IgG
antibodies remained relatively stable up to 115
days PSO in both biofluids. Importantly, IgG
responses in saliva and serum were correlated,
suggesting that antibodies in the saliva may
serve as a surrogate measure of systemic
immunity." |
|
127) The
T-cell response to SARS-CoV-2: kinetic and
quantitative aspects and the case for their
protective role, Bertoletti, 2021 |
"Early appearance,
multi-specificity and functionality of
SARS-CoV-2-specific T cells are associated with
accelerated viral clearance and with protection
from severe COVID-19." |
|
128) The
longitudinal kinetics of antibodies in COVID-19
recovered patients over 14 months, Eyran,
2020 |
"Found a
significantly faster decay in naïve vaccinees
compared to recovered patients suggesting that
the serological memory following natural
infection is more robust compared to
vaccination. Our data highlights the differences
between serological memory induced by natural
infection vs. vaccination." |
|
129) Continued
Effectiveness of COVID-19 Vaccination among
Urban Healthcare Workers during Delta Variant
Predominance, Lan, 2021 |
"Followed a
population of urban Massachusetts HCWs... we
found no re-infection among those with prior
COVID-19, contributing to 74,557
re-infection-free person-days, adding to the
evidence base for the robustness of naturally
acquired immunity." |
|
130) Immunity
to COVID-19 in India through vaccination and
natural infection, Sarraf, 2021 |
"Compared the
vaccination induced immune response profile with
that of natural infection, evaluating thereby if
individuals infected during the first wave
retained virus specific immunity... the overall
immune response resulting from natural infection
in and around Kolkata is not only to a certain
degree better than that generated by
vaccination, especially in the case of the Delta
variant, but cell mediated immunity to
SARS-CoV-2 also lasts for at least ten months
after the viral infection." |
|
131) Asymptomatic
or mild symptomatic SARS-CoV-2 infection elicits
durable neutralizing antibody responses in
children and adolescents, Garrido, 2021 |
"Evaluated humoral
immune responses in 69 children and adolescents
with asymptomatic or mild symptomatic SARS-CoV-2
infection. We detected robust IgM, IgG, and IgA
antibody responses to a broad array of
SARS-CoV-2 antigens at the time of acute
infection and 2 and 4 months after acute
infection in all participants. Notably, these
antibody responses were associated with
virus-neutralizing activity that was still
detectable 4 months after acute infection in 94%
of children. Moreover, antibody responses and
neutralizing activity in sera from children and
adolescents were comparable or superior to those
observed in sera from 24 adults with mild
symptomatic infection. Taken together, these
findings indicate that children and adolescents
with mild or asymptomatic SARS-CoV-2 infection
generate robust and durable humoral immune
responses that can likely contribute to
protection from reinfection." |
|
132) T
cell response to SARS-CoV-2 infection in humans:
A systematic review, Shrotri, 2021 |
"Symptomatic adult
COVID-19 cases consistently show peripheral T
cell lymphopenia, which positively correlates
with increased disease severity, duration of RNA
positivity, and non-survival; while asymptomatic
and paediatric cases display preserved counts.
People with severe or critical disease generally
develop more robust, virus-specific T cell
responses. T cell memory and effector function
has been demonstrated against multiple viral
epitopes, and, cross-reactive T cell responses
have been demonstrated in unexposed and
uninfected adults, but the significance for
protection and susceptibility, respectively,
remains unclear." |
|
133) Severity
of SARS-CoV-2 Reinfections as Compared with
Primary Infections, Abu-Raddad,
2021 |
"Reinfections had 90% lower odds of resulting in
hospitalization or death than primary
infections. Four reinfections were severe enough
to lead to acute care hospitalization. None led
to hospitalization in an ICU, and none ended in
death. Reinfections were rare and were generally
mild, perhaps because of the primed immune
system after primary infection." |
|
134) Assessment
of the Risk of Severe Acute Respiratory Syndrome
Coronavirus 2 (SARS-CoV-2) Reinfection in an
Intense Re-exposure Setting, Abu-Raddad,
2021 |
"SARS-CoV-2 reinfection can occur but is a rare
phenomenon suggestive of protective immunity
against reinfection that lasts for at least a
few months post primary infection." |
|
135) Increased
risk of infection with SARS-CoV-2 Beta, Gamma,
and Delta variant compared to Alpha variant in
vaccinated individuals, Andeweg, 2021 |
"Analyzed 28,578
sequenced SARS-CoV-2 samples from individuals
with known immune status obtained through
national community testing in the Netherlands
from March to August 2021. They found evidence
for an "increased risk of infection by the Beta
(B.1.351), Gamma (P.1), or Delta (B.1.617.2)
variants compared to the Alpha (B.1.1.7) variant
after vaccination. No clear differences were
found between vaccines. However, the effect was
larger in the first 14-59 days after complete
vaccination compared to 60 days and longer. In
contrast to vaccine-induced immunity, no
increased risk for reinfection with Beta, Gamma
or Delta variants relative to Alpha variant was
found in individuals with infection-induced
immunity." |
