Pfizer and BioNTech announce Phase 3 Trial data showing high efficacy of a booster dose of their COVID-19 vaccine

Oct. 25, 2021

Pfizer Inc. and BioNTech SE announced topline results from a Phase 3 randomized, controlled trial evaluating the efficacy and safety of a 30-µg booster dose of the Pfizer-BioNTech COVID-19 Vaccine in more than 10,000 individuals 16 years of age and older, according to their release.

In the trial, a booster dose administered to individuals who previously received the Pfizer-BioNTech primary two-dose series restored vaccine protection against COVID-19 to the high levels achieved after the second dose, showing a relative vaccine efficacy of 95.6% when compared to those who did not receive a booster. These are the first efficacy results from any randomized, controlled COVID-19 vaccine booster trial.

All trial participants previously completed the primary two-dose series of the Pfizer-BioNTech vaccine, and then were randomized 1:1 to receive either a 30-µg booster dose (the same dosage strength as those in the primary series) or placebo. The median time between second dose and administration of the booster dose or placebo was approximately 11 months.

Symptomatic COVID-19 occurrence was measured from at least 7 days after booster or placebo, with a median follow-up of 2.5 months. During the study period, there were 5 cases of COVID-19 in the booster group, and 109 cases in the non-boosted group. The observed relative vaccine efficacy of 95.6% (95% CI: 89.3, 98.6) reflects the reduction in disease occurrence in the boosted group versus the non-boosted group in those without evidence of prior SARS-CoV-2 infection.

Median age of participants was 53 years, with 55.5% of participants between 16 and 55 years, and 23.3% of participants 65 years and older. Multiple subgroup analyses showed efficacy was consistent irrespective of age, sex, race, ethnicity, or comorbid conditions.

The adverse event profile was generally consistent with other clinical safety data for the vaccine, with no safety concerns identified.

Pfizer and BioNTech plan to submit detailed results from the trial for peer-reviewed publication. The companies also plan to share these data with the U.S. Food and Drug Administration, European Medicines Agency, and other regulatory agencies around the world as soon as possible.

Pfizer release

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