81 Research Studies Confirm Natural Immunity to COVID ‘Equal’ or ‘Superior’ to Vaccine Immunity

The Brownstone Institute lists 81 of the highest-quality, complete, most robust scientific studies and evidence reports/position statements on natural immunity as compared to the COVID-19 vaccine-induced immunity.


Paul Elias Alexander, Ph.D.

We should not force COVID vaccines on anyone when the evidence shows that naturally acquired immunity is equal to or more robust and superior to existing vaccines. Instead, we should respect the right of the bodily integrity of individuals to decide for themselves.

Public health officials and the medical establishment with the help of the politicized media are misleading the public with assertions that the COVID-19 shots provide greater protection than natural immunity.

Centers for Disease Control and Prevention (CDC) Director Rochelle Walensky, for example, was deceptive in her October 2020 published LANCET statement that “there is no evidence for lasting protective immunity to SARS-CoV-2 following natural infection” and that “the consequence of waning immunity would present a risk to vulnerable populations for the indefinite future.”

Immunology and virology 101 have taught us over a century that natural immunity confers protection against a respiratory virus’s outer coat proteins, and not just one, e.g., the SARS-CoV-2 spike glycoprotein.

There is even strong evidence for the persistence of antibodies. Even the CDC recognizes natural immunity for chicken-pox and measles, mumps and rubella, but not for COVID-19.

The vaccinated are showing viral loads (very high) similar to the unvaccinated, and the vaccinated are as infectious. Riemersma et al. also report Wisconsin data that corroborate how the vaccinated individuals who get infected with the Delta variant can potentially (and are) transmit(ting) SARS-CoV-2 to others (potentially to the vaccinated and unvaccinated).

This troubling situation of the vaccinated being infectious and transmitting the virus emerged in seminal nosocomial outbreak papers by Chau et al. (HCWs in Vietnam), the Finland hospital outbreak (spread among HCWs and patients), and the Israel hospital outbreak (spread among HCWs and patients).

These studies also revealed that the personal protective equipment (PPE) and masks were essentially ineffective in the healthcare setting. Again, the Marek’s disease in chickens and the vaccination situation explains what we are potentially facing with these leaky vaccines (increased transmission, faster transmission, and more ‘hotter’ variants).

Moreover, existing immunity should be assessed before any vaccination, via an accurate, dependable and reliable antibody test (or T cell immunity test) or be based on documentation of prior infection (a previous positive PCR or antigen test). Such would be evidence of immunity that is equal to that of vaccination and the immunity should be provided the same societal status as any vaccine-induced immunity.

This will function to mitigate the societal anxiety with these forced vaccine mandates and societal upheaval due to job loss, denial of societal privileges etc. Tearing apart the vaccinated and the unvaccinated in a society — separating them — is not medically or scientifically supportable.

The Brownstone Institute previously documented 30 studies on natural immunity as it relates to COVID-19.

This follow-up chart is the most updated and comprehensive library list of 81 of the highest-quality, complete, most robust scientific studies and evidence reports/position statements on natural immunity as compared to the COVID-19 vaccine-induced immunity and allows you to draw your own conclusion.

I’ve benefited from the input of many to put this together, especially my co-authors:

  • Dr. Harvey Risch, M.D., Ph.D. (Yale School of Public Health)

  • Dr. Howard Tenenbaum, Ph.D. ( Faculty of Medicine, University of Toronto)

  • Dr. Ramin Oskoui, M.D. (Foxhall Cardiology, Washington)

  • Dr. Peter McCullough, M.D. (Truth for Health Foundation, Texas)

  • Dr. Parvez Dara, M.D. (consultant, Medical Hematologist and Oncologist)

Evidence on natural immunity versus COVID-19 vaccine induced immunity as of Oct. 15:

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.

“There 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) …