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Protection Against COVID-19 by BNT162b2 Booster Across Age Groups
Quick Takes
- This is an observational study leveraging the Israeli Ministry of Health database and data of over 4.5 million Israelis eligible for the BNT162b2 booster dose.
- The authors estimated the effectiveness of the booster dose in reducing the rate of confirmed infections, severity of illness, and mortality across age groups.
- Overall, the booster dose was strongly associated with reduced confirmed SARS-CoV-2 infection, severe COVID-19, and mortality across all age groups.
Study Questions:
How effective is the BNT162b2 (Pfizer–BioNTech) booster at reducing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection across age groups?
Methods:
This observational study leverages the Israeli Ministry of Health database and examines data on 4,696,865 persons ≥16 years of age who had received two doses of BNT162b2 ≥5 months earlier to the approval of the booster dose (July 30, 2021). The authors compared the rates of confirmed coronavirus disease 2019 (COVID-19), severe illness, and death among those who had received a booster dose ≥12 days earlier (booster group) with the rates among those who had not received a booster (nonbooster group). Analyses were stratified according to age groups (80+, 70-79, 60-69, 50-59, 40-49, 30-39, 16-29 years). The primary analysis examined the rate of confirmed infection, severe illness, and death ≥12 days after the booster. A secondary analysis examined these outcomes occurring ≥3 days post-booster dose (early post-booster dose).
Results:
The nonbooster group included 98 million person-days, with 83,481 confirmed infections, 1,171 cases of severe illness, and 298 deaths. The booster group included approximately 104 million person-days, with 6,160 confirmed infections, 175 cases of severe illness, and 35 deaths. The early postbooster group included approximately 17 million person-days, with 8,880 confirmed infections, 136 cases of severe illness, and 46 deaths.
The rate of confirmed infection was lower in the booster group than in the nonbooster group by a factor of approximately 10 (range across five age groups, 9.0-17.2). The rates of severe illness were lower in the booster group by a factor of 17.9 (95% confidence interval [CI], 15.1-21.2). Effect sizes for infection rates and severe illness were overall similar across age groups. Among those ≥60 years of age, mortality was lower by a factor of 14.7 (95% CI, 10.0-21.4). Effect sizes for all reported associations were lower in the early post-booster group (secondary analysis) compared to the booster group.
Conclusions:
A booster dose of the BNT162b2 vaccine was associated with a 10-fold lower rate of confirmed SARS-CoV-2 infection and 18-fold lower rate of severe illness, with similar effect size across age groups.
Perspective:
This study specifically examines the effectiveness of the BNT162b2 booster dose in reducing confirmed infection and severe COVID-19 across age groups among adults (≥16 years). Similar to findings from clinical trials of primary vaccine doses, the booster was indeed effective across all age groups, specifically for confirmed infection and severe illness. The nonrandomized and observational nature cannot address confounding and detection biases and participants’ risk avoidance behavior. Nevertheless, findings are reassuring and consistent with that of clinical trials as well as prior data surrounding the effectiveness of booster doses. These data are important to inform public health policy and promotion of booster vaccination programs.
Clinical Topics: COVID-19 Hub, Prevention
Keywords: Coronavirus Infections, COVID-19, Critical Illness, Health Policy, Immunization, Secondary, Israel, Primary Prevention, RNA, Viral, SARS-CoV-2, Vaccination, Vaccine Potency
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