Natural immunity to COVID is real and long-lasting.

It appears that an unknown number of people had natural immunity to COVID-19 from exposure to SARS or previous coronaviruses.

Study: Covid-19: Do many people have pre-existing immunity?

“Overall, our results indicate that mild infection with SARS-CoV-2 induces robust antigen-specific, long-lived humoral immune memory in humans.” 


“Individuals who have recovered from COVID-19 have a substantially lower risk of reinfection with SARS-CoV-2”

 SARS-CoV-2 infection induces long-lived bone marrow plasma cells in humans

“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.”

SARS-CoV-2 infection rates of antibody-positive compared with antibody-negative health-care workers in England: a large, multicentre, prospective cohort study (SIREN)

“Overall, positive baseline anti-spike antibodies were associated with lower rates of PCR-positivity (with or without symptoms) (adjusted rate ratio 0.24 [95%CI 0.08-0.76, p=0.015]). Rate ratios were similar using anti-nucleocapsid IgG alone or combined with anti-spike IgG to determine baseline status.”

Antibodies to SARS-CoV-2 are associated with protection against reinfection

“This quantitative study of plasma cell longevity demonstrates that plasma cells can survive for periods longer than 1 year. In addition, this study also relates the lifespan of antigen-specific plasma cells located in different anatomical sites to the level of specific antibody observed in the serum.”

Humoral Immunity Due to Long-Lived Plasma Cells

“Taken together, these results show that antibody responses, especially IgG antibody, were not only durable in the vast majority of patients in the 250 day period, but also that the bi-phasic decay curve suggests the generation of longer lived plasma cells producing antibody to the SARS-CoV-2 spike protein.”


“these data showing such stable antibody titers are best explained by the persistence of long-lived plasma cells in the bone marrow many years after infection.”


“Taken together, these results show that people infected with SARS-CoV-2 may have also have some heightened immunity against the common human betacoronaviruses and more importantly against SARS-CoV-1.”


“Taken together, our findings show that induction of neutralizing antibodies occurs in the majority of COVID-19 patients. These neutralizing antibodies can persist over the 8–9 month period following infection, and show a correlation with spike and RBD binding IgG.”


“That the CD8+ T cell differentiation program after COVID-19 infection resembles what is seen after YFV infection of human suggests that COVID-19 patients may also generate long-lived CD8+ T cell memory.”


“Our study demonstrates the considerable immune heterogeneity in the generation of potentially protective response against SARS-CoV-2, and by focusing on the dynamics and maintenance of B and T cell memory responses, we were able to identify features of these early cellular responses that can forecast the durability of a potentially effective antibody response.”

Longitudinal analysis shows durable and broad immune memory after SARS-CoV-2 infection with persisting antibody responses and memory B and T cells

How Long Does Natural Immunity Last?

At Least: