Here are 16 studies that show that Natural Immunity for those who have recovered from Covid-19 is robust. These studies will be provided with a basic summary of the findings, with minimal commentary. Direct links to the studies are provided so the reader can explore the findings themselves.
Natural Immunity Studies
1. Comparing SARS-CoV-2 natural immunity to vaccine-induced immunity: reinfections versus breakthrough infections
"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 two-dose vaccine-induced immunity. Individuals who were both previously infected with SARS-CoV-2 and given a single dose of the vaccine gained additional protection against the Delta variant."
Study Article: https://www.medrxiv.org/content/10.1101/2021.08.24.21262415v1
2. Discrete Immune Response Signature to SARS-CoV-2 mRNA Vaccination Versus Infection
New York University - May 3, 2021
"While 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."
Study Article: https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3838993
3. SARS-CoV-2 infection induces long-lived bone marrow plasma cells in humans
Washington University - May 24, 2021
"Overall, our results indicate that mild infection with SARS-CoV-2 induces robust antigen-specific, long-lived humoral immune memory in humans."
Study Article: https://www.nature.com/articles/s41586-021-03647-4
4. Necessity of COVID-19 vaccination in previously infected individuals
Cleveland Clinic - June 19, 2021
"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."
Study Article: https://www.medrxiv.org/content/10.1101/2021.06.01.21258176v3
5. Longitudinal analysis shows durable and broad immune memory after SARS-CoV-2 infection with persisting antibody responses and memory B and T cells
Fred Hutchinson Cancer Research Center - July 14, 2021
"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."
Study Article: https://www.cell.com/cell-reports-medicine/fulltext/S2666-3791(21)00203-2#%20
6. Single cell profiling of T and B cell repertoires following SARS-CoV-2 mRNA vaccine
California University, Irvine - July 21, 2021
"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. Our study highlights a coordinated adaptive immune response where early CD4 T cell responses facilitate the development of the B cell response and substantial expansion of effector CD8 T cells, together capable of contributing to future recall responses."
Study Article: https://www.biorxiv.org/content/10.1101/2021.07.14.452381v1
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
California University, San Francisco - May 12, 2021
"In infection-naïve individuals, the second dose boosted the quantity but not quality of the T cell response, while in convalescents the second dose helped 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."
Study Article: https://www.biorxiv.org/content/10.1101/2021.05.12.443888v1
8. Large-scale study of antibody titer decay following BNT162b2 mRNA vaccine or SARS-CoV-2 infection
Israeli Study - August 22, 2021
"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."
Study Article: https://www.medrxiv.org/content/10.1101/2021.08.19.21262111v1