On Oct. 21, 2021, Pfizer and BioNTech announced topline results from a Phase 3 randomized, controlled trial evaluating the efficacy and safety of a 30-ﾵg booster dose of the Pfizer-BioNTech COVID-19 Vaccine in more than 10,000 individuals 16 years of age and older.

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 were the first efficacy results from any randomized, controlled COVID-19 vaccine booster trial.