Topline results were announced from a phase 3 trial evaluating the efficacy and safety of a booster dose of the Pfizer-BioNTech COVID-19 vaccine in individuals 16 years of age and older.

The randomized, controlled trial included more than 10,000 individuals who previously completed the primary 2-dose series with the Pfizer-BioNTech COVID-19 vaccine. Patients were randomly assigned 1:1 to receive either a 30mcg booster dose of the Pfizer-BioNTech COVID-19 vaccine or placebo. The median time between the second dose and the booster dose or placebo was approximately 11 months. 

The median age of the trial population was 53 years, with 55.5% of participants between 16 and 55 years of age; 23.3% of participants were 65 years of age and older. The occurrence of symptomatic COVID-19 was measured from at least 7 days after the booster or placebo dose, with a median follow-up time of 2.5 months. 

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There were 5 cases of COVID-19 reported in the booster dose group compared with 109 cases in the placebo group, which correlated with an observed relative vaccine efficacy of 95.6% (95% CI, 89.3-98.6) in the boosted vs nonboosted group among those without evidence of prior SARS-CoV-2 infection. Vaccine efficacy was consistent regardless of age, sex, race, ethnicity, or comorbid conditions. The safety profile of the booster dose was generally consistent with other clinical safety data for the vaccine.

Detailed trial data will be submitted for peer-reviewed publication and shared with the Food and Drug Administration (FDA).

“These results provide further evidence of the benefits of boosters as we aim to keep people well protected against this disease,” said Albert Bourla, Chairman and CEO, Pfizer. “In addition to our efforts to increase global access and uptake among the unvaccinated, we believe boosters have a critical role to play in addressing the ongoing public health threat of this pandemic.”

The FDA authorized the booster dose of the Pfizer-BioNTech COVID-19 vaccine for emergency use in September 2021 for individuals 65 years of age and older, individuals 18 through 64 years of age at high risk of severe COVID-19, and individuals 18 through 64 years of age with frequent institutional or occupational exposure to SARS-CoV-2.


Pfizer and BioNTech announce phase 3 trial data showing high efficacy of a booster dose of their COVID-19 vaccine. News release. Pfizer Inc. and BioNTech SE. Accessed October 21, 2021.

This article originally appeared on MPR