Efficacy of BNT162b2 mRNA Covid-19 Vaccine Through 6 Months

Quick Takes

  • This manuscript reports 6 months of safety and efficacy analyses of the BNT162b2 phase 2-3 multinational randomized trial.
  • At 6 months post-vaccination, vaccine efficacy against SARS-CoV-2 infection was 91.3% (95% CI, 89.0-93.2), and 96.7% (95% CI, 80.3-99.9) for severe disease.
  • No new serious adverse events were attributed to the BNT162b2 at 6 months.

Study Questions:

What is the effectiveness and safety of the BNT162b2 messenger RNA (mRNA) vaccine (Pfizer–BioNTech) against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) at 6 months post-vaccination?


This manuscript reports the 6 months of effectiveness and safety results from the randomized, placebo-controlled, observer-blinded, phase 2-3 trial of the BNT162b2 vaccine. This study specifically included participants ≥16 years of age. As a reminder, participants of the trial were randomly assigned in a 1:1 ratio to receive two 30-μg intramuscular injections or saline placebo 21 days apart. The coprimary endpoints were laboratory-confirmed SARS-CoV-2 infection and safety at 6 months after the second dose. Efficacy against severe coronavirus disease 2019 (COVID-19) was also assessed.


Between July 27, 2020, and October 29, 2020, a total of 44,165 participants underwent randomization at 152 sites (130 sites in the United States, one site in Argentina, two sites in Brazil, four sites in South Africa, six sites in Germany, and nine sites in Turkey) in the phase 2-3 portion of the trial. Of these participants, 44,060 received at least one dose of BNT162b2 (n = 22,030) or placebo (n = 22,030), and 98% received the second dose. 55% of the participants had 6 months of follow-up. Of those, 49% of the participants were female, 82% were White, 10% were Black, and 26% were Hispanic or Latinx; the median age was 51 years; and 21% had at least one underlying medical condition. Overall, there was a small and gradual decline in efficacy. At 6 months post-second dose, vaccine efficacy against SARS-CoV-2 infection was 91.3% (95% confidence interval [CI], 89.0-93.2), and 96.7% (95% CI, 80.3-99.9) for severe disease. Efficacy ranged from 86% to 100% across countries and in populations with diverse ages, sexes, race or ethnic groups, and risk factors for COVID-19 among participants. No new serious adverse events were considered by the investigators to be related to BNT162b2 after the data cutoff date of the previous report (2 months).


Through 6 months of follow-up and despite a gradual decline in vaccine efficacy, BNT162b2 had a favorable safety profile and was highly efficacious in preventing SARS-CoV-2 infection and severe COVID-19.


This updated report of the multinational randomized trial of the BNT162b2 vaccine provides reassuring evidence of >90% efficacy of the vaccine at 6 months of follow-up in participants who received two doses of the vaccine. It is timely, as debates on the need for a third booster shot are raging. The vaccine remained effective against variants dominant at the time including the beta-variant (predominant in South Africa), which is antigenically more distant than delta, against which other reports show the BNT162b2 vaccine is estimated to be ≥80% efficacious. Moreover, this study provides reassuring 6-month data on safety, which hopefully allays some of the fears regarding unexpected adverse effects attributed to the vaccine. This report does not address protection against asymptomatic infection, and subpopulations such as pregnant women and children <16 years of age.

Clinical Topics: Congenital Heart Disease and Pediatric Cardiology, Prevention, CHD and Pediatrics and Arrhythmias, CHD and Pediatrics and Quality Improvement

Keywords: Adolescent, Coronavirus, COVID-19, COVID-19 Vaccines, Primary Prevention, Risk Factors, RNA, Messenger, SARS-CoV-2, Vaccination, Vaccine Potency

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