Natural Immunity Resources
One-year sustained cellular and humoral immunities of COVID-19 convalescents (Oct 5, 2021) “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. Furthermore, both antibody and T-cell memory levels of the convalescents were positively associated with their disease severity.”
Comparing SARS-CoV-2 natural immunity to vaccine-induced immunity: reinfections versus breakthrough infections (Aug. 25, 2021)
This study demonstrated that natural immunity confers longer lasting and stronger protection against infection, symptomatic disease and hospitalization caused by the Delta variant of SARS-CoV-2, compared to the BNT162b2 (Pfizer) two-dose vaccine-induced immunity. SARS-CoV-2-naïve vaccinees had a 13.06-fold (95% CI, 8.08 to 21.11) increased risk for breakthrough infection with the Delta variant compared to those previously infected, when the first event (infection or vaccination) occurred during January and February of 2021. The increased risk was significant (P<0.001) for symptomatic disease as well. When allowing the infection to occur at any time before vaccination (from March 2020 to February 2021), evidence of waning natural immunity was demonstrated, though SARS-CoV-2 naïve vaccinees had a 5.96-fold (95% CI, 4.85 to 7.33) increased risk for breakthrough infection and a 7.13-fold (95% CI, 5.51 to 9.21) increased risk for symptomatic disease. SARS-CoV-2-naïve vaccinees were also at a greater risk for COVID-19-related-hospitalizations compared to those that were previously infected. You are 27x more likely to develop COVD symptoms if you are vaccinated than unvaccinated w/natural immunity you gained.
Large-scale study of antibody titer decay following BNT162b2 mRNA vaccine or SARS-CoV-2 infection (Aug. 22, 2021)
Results: 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. Six months after BNT162b2 vaccination 16.1% subjects had antibody levels below the seropositivity threshold of <50 AU/mL, while only 10.8% of convalescent patients were below <50 AU/mL threshold after 9 months from SARS-CoV-2 infection.
Conclusions: 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.
Reduced Risk of Reinfection with SARS-CoV-2 After COVID-19 Vaccination — Kentucky, May–June 2021 (Aug 6, 2021)
Among Kentucky residents infected with SARS-CoV-2 in 2020, vaccination status of those “reinfected” during May–June 2021 was compared with that of residents who were not reinfected. In this case-control study, being unvaccinated was associated with 2.34 times the odds of reinfection compared with being fully vaccinated.
Limitations: “Reinfections” were confirmed using an antigen test and not the whole genome sequencing needed to confirm that the reinfection was caused by a distinct virus and was not related to the first infection (Note: although there is a gap in time between 2020 initial infection and May/June 2021 “reinfection”, the majority of the cases for reinfection were very late in 2020 which does not make sense; 82.9% were from October to December; almost 70% in November/December). Second, vaccinated people are less likely to get tested for COVID-19, which could overestimate the relationship between lack of vaccination and reinfection. Third, the sample size was small. Fourth, perhaps most importantly, even if there was reinfection, there is no indication whether the reinfected patients were symptomatic, hospitalized, or died (noting that vaccine breakthrough cases are only counted if hospitalization or death; this study uses a much different standard).
Antibody Evolution after SARS-CoV-2 mRNA Vaccination (July 29, 2021)
“Severe acute respiratory syndrome coronavirus 2 (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…We conclude that memory antibodies selected over time by natural infection have greater potency and breadth than antibodies elicited by vaccination.”
Persistence of neutralizing antibodies a year after SARS-CoV-2 infection (July 19, 2021)
Abstract: We assessed the persistence of serum antibodies following wild-type SARS-CoV-2 infection six and twelve months after diagnosis in 367 individuals of whom 13% had severe disease requiring hospitalization. We determined the SARS-CoV-2 spike (S-IgG) and nucleoprotein IgG concentrations and the proportion of subjects with neutralizing antibodies (NAb). We also measured the NAb titers among a smaller subset of participants (n=78) against a wild-type virus (B.1) and three variants of concern (VOCs): Alpha (B.1.1.7), Beta (B.1.351) and Delta (B.1.617.2). We found that NAb against the wild-type virus and S-IgG persisted in 89% and 97% of subjects for at least twelve months after infection, respectively. IgG and NAb levels were higher after severe infection. NAb titers were significantly lower against variants compared to the wild-type virus.
Natural immunity against COVID-19 significantly reduces the risk of reinfection: findings from a cohort of sero-survey participants (July 19, 2021)
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. Interestingly, from the 127 sero-negative individuals who later contracted COVID-19 infection, 30 needed hospitalization, out of which 12 were on oxygen therapy, four in ICU and one was on ventilator. At the other hand, from the 3 sero-positives re-infected with COVID-19, one had hospitalization, but did not require oxygen support or critical care. These findings reinforce the strong plausibility that 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. [~2.8% risk of hospitalization if seronegative for antibodies]
Longitudinal analysis shows durable and broad immune memory after SARS-CoV-2 infection with persisting antibody responses and memory B and T cells (July 14, 2021)
Emory: Evaluated 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. SARS-CoV-2 infection also boosts antibody titers to SARS-CoV-1 and common beta coronaviruses. In addition, spike-specific IgG+ memory B cells persist, which bodes well for a rapid antibody response upon virus re-exposure or vaccination. Virus-specific CD4+ and CD8+ T cells are polyfunctional and maintained with an estimated half-life of 200 days. Interestingly, CD4+ T cell responses equally target several SARS-CoV-2 proteins, whereas the CD8+ T cell responses preferentially target the nucleoprotein, highlighting the potential importance of including the nucleoprotein in future vaccines. Taken together, these results suggest that broad and effective immunity may persist long-term in recovered COVID-19 patients.
Anti-spike antibody response to natural SARS-CoV-2 infection in the general population (July 5, 2021)
UK: 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.
Necessity of COVID-19 vaccination in previously infected individuals (June 5, 2021)
Cleveland Clinic: "Among the 52238 included employees, 1359 (53%) of 2579 previously infected subjects remained unvaccinated, compared with 22777 (41%) of 49659 not previously infected. 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. In a Cox proportional hazards regression model, after adjusting for the phase of the epidemic, vaccination was associated with a significantly lower risk of SARS-CoV-2 infection among those not previously infected (HR 0.031, 95% CI 0.015 to 0.061) but not among those previously infected (HR 0.313, 95% CI 0 to Infinity).
Conclusions: Individuals who have had SARS-CoV-2 infection are unlikely to benefit from COVID-19 vaccination, and vaccines can be safely prioritized to those who have not been infected before."
Breakthrough Infections of SARS-CoV-2 Gamma Variant in Fully Vaccinated Gold Miners, French Guiana, 2021 (July 21, 2021 electronic; October 2021 print)
CDC - Gamma variant: The attack rate was 15/25 (60.0%) in fully vaccinated miners, 6/15 (40.0%) in those partially vaccinated or with a history of COVID-19, and 3/4 (75%) in those not vaccinated. Attack rate was 0/6 among persons with a previous history of COVID-19 versus 63.2% among those with no previous history. No other factors were found to be associated with the risk for infection.
UCLA - Incidence of Severe Acute Respiratory Syndrome Coronavirus-2 infection among previously infected or vaccinated employees (July 8, 2021)
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.
Qatar: Association of Vaccination and of Prior Infection With Positive PCR Tests for SARS-CoV-2 (June 9, 2021)
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.
Reverse-transcribed SARS-CoV-2 RNA can integrate into the genome of cultured human cells and can be expressed in patient-derived tissues (May 25, 2021) - Natural immunity “break-through” may actually be due to persistent infection
An unresolved issue of SARS-CoV-2 disease is that patients often remain positive for viral RNA as detected by PCR many weeks after the initial infection in the absence of evidence for viral replication. We show here that SARS-CoV-2 RNA can be reverse-transcribed and integrated into the genome of the infected cell and be expressed as chimeric transcripts fusing viral with cellular sequences. Importantly, such chimeric transcripts are detected in patient-derived tissues. Our data suggest that, in some patient tissues, the majority of all viral transcripts are derived from integrated sequences.
SARS-CoV-2 infection induces long-lived bone marrow plasma cells in humans (May 24, 2021; NIH funded study out of Washington University))
In convalescent individuals who had experienced mild SARS-CoV-2 infections (n = 77), levels of serum anti-SARS-CoV-2 spike protein (S) antibodies declined rapidly in the first 4 months after infection and then more gradually over the following 7 months, remaining detectable at least 11 months after infection. Overall, our results indicate that mild infection with SARS-CoV-2 induces robust antigen-specific, long-lived humoral immune memory in humans.
WHO: COVID-19 natural immunity (May 10, 2021)
Large cohort studies have reported that 90-99% of SARS-CoV-2 infected individuals develop neutralizing antibodies within 2-4 weeks after infection. 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). Studies aimed to detect immunological memory including the assessment of cellular immunity by testing for the presence of memory B cells, and CD4+ and CD8+ T cells, observed robust immunity at 6 months post-infection in 95% of subjects under study, which included individuals with asymptomatic, mild, moderate and severe infections.
Longitudinal analysis shows durable and broad immune memory after SARS-CoV-2 infection with persisting antibody responses and memory B and T cells (April 27, 2021)
We evaluated 254 COVID-19 patients longitudinally from early infection and for eight months thereafter and found a predominant broad-based immune memory response. SARS-CoV-2 spike binding and neutralizing antibodies exhibited a bi-phasic decay with an extended half-life of >200 days suggesting the generation of longer-lived plasma cells. In addition, there was a sustained IgG+ memory B cell response, which bodes well for a rapid antibody response upon virus re-exposure. Polyfunctional virus-specific CD4+ and CD8+ T cells were also generated and maintained with an estimated half-life of 200 days. Interestingly, the CD4+ T cell response equally targeted several SARS-CoV-2 proteins, whereas the CD8+ T cell response preferentially targeted the nucleoprotein, highlighting the importance of including the nucleoprotein as a potential vaccine antigen. Taken together, these results suggest that broad and effective immunity may persist long-term in recovered COVID-19 patients.
SARS-CoV-2 antibody-positivity protects against reinfection for at least seven months with 95% efficacy (April 27, 2021)
Applying the viral-genome-sequencing confirmation rate, the incidence rate of reinfection was estimated at 0.66 per 10,000 person-weeks (95% CI: 0.56–0.78). Incidence rate of reinfection versus month of follow-up did not show any evidence of waning of immunity for over seven months of follow-up. Meanwhile, in the complement cohort of 149,923 antibody-negative persons followed for a median of 17.0 weeks (range: 0–45.6), incidence rate of infection was estimated at 13.69 per 10,000 person-weeks (95% CI: 13.22–14.14). Efficacy of natural infection against reinfection was estimated at 95.2% (95% CI: 94.1–96.0%). Reinfections were less severe than primary infections. Only one reinfection was severe, two were moderate, and none were critical or fatal. Most reinfections (66.7%) were diagnosed incidentally through random or routine testing, or through contact tracing
Israel:
Protection of previous SARS-CoV-2 infection is similar to that of BNT162b2 vaccine protection: A three-month nationwide experience from Israel (April 24, 2021)
"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]). Our results question the need to vaccinate previously-infected individuals."
Immune Memory in Mild COVID-19 Patients and Unexposed Donors Reveals Persistent T Cell Responses After SARS-CoV-2 Infection (Mar 11, 2021)
We 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.
SARS-CoV-2 re-infection risk in Austria (Feb 21, 2021)
Observed a 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.
Lasting immunity found after recovery from COVID-19 (January 26, 2021)
The immune systems of more than 95% of people who recovered from COVID-19 had durable memories of the virus up to eight months after infection. The results provide hope that people receiving SARS-CoV-2 vaccines will develop similar lasting immune memories after vaccination.
What we know about covid-19 reinfection so far (Jan 19, 2021)
With most coronaviruses, recovery confers a degree of immunity to reinfection. But a small number of patients have caught covid-19 for a second time. Reinfections tend to be milder, but there have been a couple reported deaths.
Immunological memory to SARS-CoV-2 assessed for greater than six months after infection (Nov 16, 2020; note pharma COIs)
We analyzed multiple compartments of circulating immune memory to SARS-CoV-2 in 185 COVID-19 cases, including 41 cases at ≥6 months post-infection. Spike IgG was relatively stable over 6+ months. Spike-specific memory B cells were more abundant at 6 months than at 1 month. SARS-CoV-2-specific CD4+ T cells and CD8+ T cells declined with a half-life of 3-5 months. By studying antibody, memory B cell, CD4+ T cell, and CD8+ T cell memory to SARS-CoV-2 in an integrated manner, we observed that each component of SARS-CoV-2 immune memory exhibited distinct kinetics.
T Cell Immunity - SARS-CoV-2-specific T cell immunity in cases of COVID-19 and SARS, and uninfected controls (July 15, 2020)
Patients (n = 23) who recovered from SARS (the disease associated with SARS-CoV infection) 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.
Risks of Vaccination
OpenVAERS (Note: VAERS is a passive reporting system established by the CDC. Reports are not confirmed and represent correlation, not necessarily causation. Adverse events are known to be significantly underreported).
Research also shows increased risk of vaccination for those with natural immunity. Vaccine side-effects and SARS-CoV-2 infection after vaccination in users of the COVID Symptom Study app in the UK: a prospective observational study (April 27, 2021)
Systemic side-effects were more common (1·6 times after the first dose of ChAdOx1 nCoV-19 and 2·9 times after the first dose of BNT162b2) among individuals with previous SARS-CoV-2 infection than among those without known past infection.
Previous COVID-19 infection but not Long-COVID is associated with increased adverse events following BNT162b2/Pfizer vaccination (April 22, 2021)
Prior COVID-19 infection but not ongoing Long-COVID symptoms were associated with an increase in the risk of self-reported adverse events following BNT162b2/Pfizer vaccination. COVID-19 illness-vaccination interval did not significantly influence AEs. The proportion reporting one moderate/severe symptom was higher in the previous COVID-19 group (56% v 47%) with fever, fatigue, myalgia-arthralgia and lymphadenopathy significantly more common.
Self-reported real-world safety and reactogenicity of COVID-19 vaccines: An international vaccine-recipient survey (March 17, 2021)
Prior COVID-19 infection was associated with increased risk of any side effect, breathlessness, flu-like illness, fatigue and local reactions. It was also associated with increased risk of severe side effects, leading to hospital care. Among 2000 people who completed an online survey after vaccination, those with a history of COVID-19 were 56% more likely to experience a severe side effect that required hospital care.
Other studies suggest that a two dose regimen may be counterproductive for those with prior infection. Differential effects of the second SARS-CoV-2 mRNA vaccine dose on T cell immunity in naive and COVID-19 recovered individuals (Aug. 3, 2021)
“Our results demonstrate that, while the second dose increases both the humoral and cellular immunity in naive individuals, COVID-19 recovered individuals reach their peak of immunity after the first dose. These results suggests that a second dose, according to the current standard regimen of vaccination, may be not necessary in individuals previously infected with SARS-CoV-2.”
Waning Vaccine Efficacy/Rates of Breakthrough Infections in the Vaccinated (Compare efficacy of natural immunity to vaccine immunity over time)
A breakthrough case refers to anyone who is diagnosed with COVID after being fully vaccinated. A person is considered fully vaccinated two weeks after receiving the second dose of either the Pfizer or Moderna COVID vaccine, or two weeks after receiving the single-dose Johnson & Johnson (J&J) vaccine. Beginning May 1, 2021, the CDC revised its system for reporting breakthrough cases, stating it would count only those cases that result in hospitalization or death. Previously, the agency had included in its breakthrough count anyone who tested positive for COVID.
CNN: Studies confirm waning immunity from Pfizer's Covid-19 vaccine (Oct. 7, 2021)
The studies, from Israel and from Qatar and published in the New England Journal of Medicine, support arguments that even fully vaccinated people need to maintain precautions against infection. One study from Israel covered 4,800 health care workers and showed antibody levels wane rapidly after two doses of vaccine "especially among men, among persons 65 years of age or older, and among persons with immunosuppression." "We found that a significant and rapid decrease in humoral response to the BNT162b2 vaccine was observed within months after vaccination." "Overall, the accumulating evidence from our study and others shows that long-term humoral response and vaccine effectiveness in previously infected persons were superior to that in recipients of two doses of vaccine," they wrote. The study was conducted from December 19, 2020, to July 9, 2021 (before Delta peak which means that efficacy could even be lower).
A second study from Qatar (Oct. 6, 2021) looked at actual infections among the highly vaccinated population of that small Gulf nation. People there mostly got Pfizer/BioNTech's vaccine, also known as BNT162b2. "BNT162b2-induced protection against infection builds rapidly after the first dose, peaks in the first month after the second dose, and then gradually wanes in subsequent months," Laith Abu-Raddad of Weill Cornell Medicine-Qatar and colleagues wrote. "The waning appears to accelerate after the fourth month, to reach a low level of approximately 20% in subsequent months," [in months 5 through 7 after the second dose] they added. Nonetheless, protection against hospitalization and death stayed at above 90%, they said.
Effectiveness of mRNA BNT162b2 COVID-19 vaccine up to 6 months in a large integrated health system in the USA (Oct. 4 2021)
A Pfizer-funded study published in The Lancet found the efficacy of the Pfizer/BioNTech COVID vaccine fell below 50% about six months after the second dose. The study found Pfizer’s vaccine was 88% effective in the first month after full vaccination but dropped to 47% effectiveness at about six months.
CDC: Effectiveness of COVID-19 Vaccines in Preventing SARS-CoV-2 Infection Among Frontline Workers Before and During B.1.617.2 (Delta) Variant Predominance — Eight U.S. Locations, December 2020–August 2021 (Aug. 27, 2021)
The vaccine effectiveness (VE) estimate was 85% among participants for whom <120 days had elapsed since completion of full vaccination compared with 73% among those for whom ≥150 days had elapsed.
During May 1–July 25, 2021, among 43,127 SARS-CoV-2 infections in residents of Los Angeles County, California, 10,895 (25.3%) were in fully vaccinated persons, 1,431 (3.3%) were in partially vaccinated persons, and 30,801 (71.4%) were in unvaccinated persons. On July 25, infection and hospitalization rates among unvaccinated persons were 4.9 and 29.2 times, respectively, those in fully vaccinated persons.
Assessed Pfizer and Moderna’s effectiveness over time against infections among nursing home residents, and found it dropped from 75% pre-Delta to 53% when Delta became dominant. The study didn’t differentiate between asymptomatic, symptomatic and severe infections.
Shedding of Infectious SARS-CoV-2 Despite Vaccination (Aug. 24, 2021)
“The SARS-CoV-2 Delta variant might cause high viral loads, is highly transmissible, and contains mutations that confer partial immune escape. Outbreak investigations suggest that vaccinated persons can spread Delta. We compared RT-PCR cycle threshold (Ct) data from 699 swab specimens collected in Wisconsin 29 June through 31 July 2021 and tested with a qualitative assay by a single contract laboratory. Specimens came from residents of 36 counties, most in southern and southeastern Wisconsin, and 81% of cases were not associated with an outbreak. During this time, estimated prevalence of Delta variants in Wisconsin increased from 69% to over 95%. Vaccination status was determined via self-reporting and state immunization records.”
CDC Studies Show Vaccine Protection Wanes Over Time, Less Effective Against Delta Variant (Auf. 19. 2021)
Transmission of SARS-CoV-2 Delta Variant Among Vaccinated Healthcare Workers, Vietnam (Aug. 10, 2021)
Oxford University Clinical Research Group, published in The Lancet, found vaccinated individuals carry 251 times the load of COVID-19 viruses in their nostrils compared to the unvaccinated.
Mayo Clinic: Comparison of two highly-effective mRNA vaccines for COVID-19 during periods of Alpha and Delta variant prevalence
In July [Delta prevalence 70%], the effectiveness against infection was considerably lower for mRNA-1273 [Moderna] (76%, 95% CI: 58-87%) with an even more pronounced reduction in effectiveness for BNT162b2 [Pfizer] (42%, 95% CI: 13-62%).
NYT: Israeli Data Suggests Possible Waning in Effectiveness of Pfizer Vaccine (July 23, 2021)
Israel says Pfizer Covid vaccine is just 39% effective as delta spreads, but still prevents severe illness (July 23, 2021)
Israel Ministry of Health just released another vaccine efficacy update due to #DeltaVariant—only 39% Pfizer VE for #COVID19 infection, 40.5% for symptomatic, 88% for hospitalization, 91% for ICU/low oxygen/ death. Source
As of September 13, 2021, the CDC had reported 15,790 breakthrough cases resulting in death and hospitalization in the United States.
Media/Other Resources on Natural Immunity
Natural Immunity and Covid-19: Twenty-Nine Scientific Studies to Share with Employers, Health Officials, and Politicians ⋆ Brownstone Institute (Oct. 10, 2021)
BMJ: Vaccinating people who have had covid-19: why doesn’t natural immunity count in the US? (Sept. 13, 2021)
Vaccinating People Who Have Had COVID-19: Why Doesn’t Natural Immunity Count in the U.S.? (Sept. 14, 2021)
The CDC’s current guidance for chickenpox, for example, does not encourage those who have contracted it to vaccinate themselves against the virus.
NCLA Represents COVID-19 Survivors in Class-Action Lawsuit Against Mich. State U. Vaccine Mandate
Having SARS-CoV-2 once confers much greater immunity than a vaccine—but vaccination remains vital
Natural immunity for the win - by Alex Berenson - Unreported Truths
Delta Variant: Natural Immunity 700% Greater Protection Than Shot, Data from Israeli Govt. Shows
WSJ Editorial Falsehood Re: Susceptibility of COVID-Recovered To Re-infection (July 20, 2021)
Neutralizing antibodies persist against SARS-CoV-2 at least a year after infection (July 19, 2021)
Researchers in Finland have conducted a study showing that in a cohort of more than 360 recovered individuals, immunoglobulin G (IgG) antibodies binding the wild-type SARS-CoV-2 spike protein persisted in 97% of patients for at least twelve months. By contrast, neutralization capacity was significantly decreased against the B.1.1.7 (alpha), B.1.351 (beta), and B.1.617.2 (delta) variants of concern that arose in the UK, South Africa and India, respectively. However, the team points out that while re-infection could occur in the absence of neutralizing antibodies, cellular immunity has been shown to less affected by mutations present in these variants and will likely provide long-term protection against severe disease.
Should People Who Have Recovered from COVID Take a Vaccine?
Forbes: Antibodies From Covid Infection Last At Least Nine Months, Study Finds (July 19, 2021)
The researchers, writing in Nature Communications, found that 98.8% of people infected in the first wave—around February/March 2020—still showed detectable levels of antibodies nine months on when tested in November. There was no difference between people who had symptomatic and asymptomatic illness, the study found. Lead author Dr. Ilaria Dorigatti said this suggests that “the strength of the immune response does not depend on the symptoms and the severity of the infection.” For some people, antibody levels actually increased between testing, indicating a boost to the immune system from another infection with the virus. The possibility of further infection could mean that people with antibodies—whether by infection or vaccination—are capable of transmitting the virus even if they are protected from disease, the researchers warned.
WSJ Op-ED - The Flimsy Evidence Behind the CDC’s Push to Vaccinate Children (July 19, 2021)
The agency overcounts Covid hospitalizations and deaths and won’t consider if one shot is sufficient.
Study shows antibody titers after natural SARS-CoV-2 infection last longer than previously thought (July 7, 2021)
A recent study by researchers from the United Kingdom (UK) revealed that antibody levels associated with protection against reinfection with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are likely to last from 1.5 to 2 years on average and that the protection from severe infection may be present for several years.
A long-term perspective on immunity to COVID (June 14, 2021)
Determining the duration of protective immunity to infection by SARS-CoV-2 is crucial for understanding and predicting the course of the COVID-19 pandemic. Clinical studies now indicate that immunity will be long-lasting. In evaluating vaccine efficacy, we should not expect the high antibody concentrations characteristic of acute immune reactions to be maintained in the memory phase. It is an old misconception, when advocating frequent revaccinations, that antibody concentrations during the acute immune reaction can be compared with those later on, to calculate an imaginary ‘half-life’ of antibody-mediated immunity. This ignores the biphasic character of the immune response (Fig. 1). The good news is that the evidence thus far predicts that infection with SARS-CoV-2 induces long-term immunity in most individuals. This provides a welcome positive note as we wait for further data on memory responses to vaccination.
Op-Ed: Quit Ignoring Natural COVID Immunity (May 28, 2021)
— Antibody testing and proof of prior infection can allow more people to return to normal
Washington University - Good news: Mild COVID-19 induces lasting antibody protection
People who have had mild illness develop antibody-producing cells that can last lifetime (May 24, 2021; study discussed linked above)
“Last fall, there were reports that antibodies wane quickly after infection with the virus that causes COVID-19, and mainstream media interpreted that to mean that immunity was not long-lived,” said senior author Ali Ellebedy, PhD, an associate professor of pathology & immunology, of medicine and of molecular microbiology. “But that’s a misinterpretation of the data. It’s normal for antibody levels to go down after acute infection, but they don’t go down to zero; they plateau. Here, we found antibody-producing cells in people 11 months after first symptoms. These cells will live and produce antibodies for the rest of people’s lives. That’s strong evidence for long-lasting immunity.”
Previous COVID-19 may cut risk of reinfection 84% (April 12, 2021)
People who had COVID-19 had an 84% lower risk of becoming reinfected and a 93% lower risk of symptomatic infection during 7 months of follow-up,
Sensitivity Levels of Various Antibody Tests
Performance characteristics of five immunoassays for SARS-CoV-2: a head-to-head benchmark comparison (Sept 23, 2020)
Abbott assay sensitivity was 92·7% (95% CI 90·2–94·8) and specificity was 99·9% (99·4–100%); for the DiaSorin assay sensitivity was 96·2% (94·2–97·7) and specificity was 98·9% (98·0–99·4); for the Oxford immunoassay sensitivity was 99·1% (97·8–99·7) and specificity was 99·0% (98·1–99·5); for the Roche assay sensitivity was 97·2% (95·4–98·4) and specificity was 99·8% (99·3–100); and for the Siemens assay sensitivity was 98·1% (96·6–99·1) and specificity was 99·9% (99·4–100%). All assays achieved a sensitivity of at least 98% with thresholds optimised to achieve a specificity of at least 98% on samples taken 30 days or more post symptom onset.
Testing for T-Cells