Heightened COVID-19 Vaccine Response following SARS-CoV-2 Infection

Kelsen, S. G.; Braverman, A.; Patel, P.; Aksoy, M. O.; Hayman, J.; Rajput, C.; Ruggieri, M.; Gentile, N.

Background: The SARS-CoV-2 mRNA vaccines now available are highly effective at preventing infection and afford the prospect of an end to the pandemic. Vaccines are in scare supply, however. Current recommendations in the United States are that subjects with a previous history of SARS-CoV-2 infection/COVID-19 disease should receive the full vaccine regimen. This is despite the fact that prior SARS-CoV-2 infection infection confers some degree of protection and that the immune response to the vaccine is not well studied. Methods: The present study compared the time course and magnitude of the humoral immune response to an mRNA SARS-CoV-2 vaccine (BNT162b2) in subjects with prior infection/COVID-19 disease (n=24) and those without prior infection (n=25). Serum anti-Spike RBD antibody and serum neutralizing activity were assessed longitudinally prior to and at 2-week intervals for 56 days post first dose of vaccine. Subjects received the standard Pfizer BNT162b2 mRNA vaccine regimen i.e., two doses of 30 mcg, 3 weeks apart. Findings: The cohort with prior COVID-19 achieved robust increases in anti-Spike IgG antibody and serum neutralizing activity compared to the SARS-CoV-2 naive cohort at day 14 post vaccine. Thereafter, the COVID-19 cohort showed relatively little further increase in humoral immunity even after the second dose such that anti-Spike IgG and neutralizing activity were similar in the 2 groups from day 28 through day 56. Conclusions: In contrast to the responses of SARS-CoV-2 naive subjects in whom a 2 dose regimen appears to be required to achieve robust immune protection, subjects with prior SARS-CoV-2 infection exhibit immune memory and have a robust response to the first dose of an mRNA vaccine. They may require only a single dose of vaccine.