BNT162b2 vaccination after SARS-CoV-2 infection decreases risk of recurrent infection
1. In a retrospective cohort study of individuals who recovered from SARS-CoV-2, BNT162b2 vaccination decreased the risk of recurrent infection.
Evidence rating level: 2 (good)
Summary of the study: The long-term efficacy and durability of immune protection provided after SARS-CoV-2 (Covid-19) infection is unclear. The aim of this retrospective cohort study was to assess whether vaccination with the BNT162b2 Covid-19 vaccine (Pfizer-BioNTech) would protect against reinfection in individuals previously infected with Covid-19. In this retrospective cohort study, the electronic medical records of patients who had previously recovered from Covid-19 in Israel were reviewed for the incidence of reinfection. Reinfection rates between individuals vaccinated with the BNT162b2 vaccine and unvaccinated individuals were compared to determine vaccine efficacy. The study found that reinfection occurred in 2.46 cases per 100,000 people per day in vaccinated people, which was significantly lower than 10.21 cases per 100,000 people per day in unvaccinated people, which gives a vaccine efficacy of 82%. Rates were similar between individuals vaccinated with one dose and those receiving two doses. Taken together, this study supports that previously infected people who also receive subsequent vaccination against Covid-19 have a lower risk of reinfection compared to those who are not vaccinated. The results of this study are limited by the retrospective design of the study, the use of irregular PCR tests and the analysis of only patients receiving the BNT162b2 vaccine.
Click to read the study in the NEJM
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In depth [retrospective cohort]: In this retrospective cohort study, 149,032 electronic medical records of people previously infected with SARS-CoV-2 (Covid-19) at a single health center in Israel were reviewed. Patients were eligible if they had recovered from a documented Covid-19 infection 100 days prior to receiving any vaccination and had not previously experienced Covid-19 reinfection. The study cohort was divided into individuals receiving at least one dose of BNT162b2 Covid-19 vaccine and unvaccinated, with the primary outcome being the incidence of reinfection with Covid-19 as determined by the chain reaction test. by polymerase (PCR). The Cox proportional hazards regression model was used to analyze the statistical differences between the two groups. Reinfections were significantly lower in the vaccinated group where 354 of 83,356 people were reinfected (2.46 cases per 100,000 people per day), compared to the unvaccinated group where 2,120 of 60,877 patients were reinfected (10 79 cases per 100,000 people per day). The adjusted hazard ratio for protection against reinfection by vaccination was 0.18 (95% confidence interval [CI], 0.16-0.20) in patients aged 16-64 years and 0.40 (95% CI, 0.24-0.64) in those older than 65 years. Vaccine efficacy was estimated at 82% (95% CI, 80-84). Reinfection rates were similar among individuals with a hazard ratio of 0.98 (95% CI, 0.64-1.5) for individuals receiving two doses versus one dose. Overall, the study supports that vaccination with the BNT162b2 vaccine confers significant protection against reinfection with Covid-19 in people already infected with Covid-19.
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