The Incidence of SARS-CoV-2 Reinfection in Persons With Naturally Acquired Immunity With and Without Subsequent Receipt of a Single Dose of BNT162b2 Vaccine: A Retrospective Cohort Study

• Published in: Annals of Internal Medicine 2022-05
• Main Authors: Gazit, Sivan, Shlezinger, Roei, Perez, Galit, Lotan, Roni, Peretz, Asaf, Ben-Tov, Amir, Herzel, Esma, Alapi, Hillel, Cohen, Dani, Muhsen, Khitam, Chodick, Gabriel, Patalon, Tal
• Format: Article
• Language: English
• DOI: 10.7326/M21-4130

Visual Abstract. A Single Dose of BNT162b2 Enhances Naturally Acquired Immunity. This study used a national database in Israel to compare incidence rates of SARS-CoV-2 reinfection in persons who were previously infected with SARS-CoV-2 but did not receive subsequent vaccination versus those who received a single dose of the BNT162b2 mRNA vaccine. * Download figure * Download PowerPoint Abstract Background: There is insufficient evidence regarding the magnitude and durability of protection conferred by a combined effect of naturally acquired immunity after SARS-CoV-2 infection and vaccine-induced immunity. Objective: To compare the incidence rate of SARS-CoV-2 reinfection in previously infected persons to that of previously infected persons who subsequently received a single dose of BNT162b2 messenger RNA vaccine. Design: A retrospective cohort study emulating a randomized controlled target trial through a series of nested trials. Setting: Nationally centralized database of Maccabi Healthcare Services, Israel. Participants: Persons with documented SARS-CoV-2 infection who did not receive subsequent SARS-CoV-2 vaccination were compared with persons with documented SARS-CoV-2 infection who received a single dose of the BNT162b2 vaccine at least 3 months after infection. Intervention: Forty-one randomized controlled trials were emulated, in which 107 413 Maccabi Healthcare Services' members aged 16 years and older were eligible for at least 1 trial. Measurements: SARS-CoV-2–related outcomes of infection, symptomatic disease, hospitalization, and death, between 2 March and 13 December 2021. Results: A statistically significant decreased risk (hazard ratio, 0.18 [95% CI, 0.15 to 0.20]) for reinfection was found among persons who were previously infected and then vaccinated versus those who were previously infected but remained unvaccinated. In addition, there was a decreased risk for symptomatic disease (hazard ratio, 0.24 [CI, 0.20 to 0.29]) among previously infected and vaccinated persons compared with those who were not vaccinated after infection. No COVID-19–related mortality cases were found. Limitation: Hybrid protection against non-Delta variants could not be inferred. Conclusion: Persons previously infected with SARS-CoV-2 gained additional protection against reinfection and COVID-19 from a subsequent single dose of the BNT162b2 vaccine. Nonetheless, even without a subsequent vaccination, reinfection appeared relatively rare. Primary Funding Source: None