Pfizer: COVID booster shot shows 95.6% efficacy

Data from Pfizer’s COVID-19 vaccine booster trial shows third shot bolsters immunity

FILE - In this Oct. 5, 2021, file photo a healthcare worker fills a syringe with the Pfizer COVID-19 vaccine at Jackson Memorial Hospital in Miami. (AP Photo/Lynne Sladky, File) (Lynne Sladky, Copyright 2021 The Associated Press. All rights reserved.)

Pfizer’s COVID-19 booster shot restores an individual’s immunity against the virus to 95.6%, according to results from their booster trial.

The drug company, which is behind the Pfizer-BioNTech vaccine, released new data Thursday from its randomized, controlled COVID vaccine booster trial -- reportedly the first results from any such kind of COVID vaccine booster study. According to officials, Pfizer’s COVID-19 vaccine efficacy was restored to 95.6% in individuals who received booster shots when compared to those who did not receive booster shots.

When initially introduced, Pfizer’s COVID vaccine showed a 95% efficacy against symptomatic illness. As virus variants, such as the delta variant, developed, the vaccines appeared to be slightly less effective: Preliminary data from Israel in July suggested that Pfizer’s vaccine had a 64% efficacy rate against the delta variant.

Booster shots were introduced after data showed that, while still effective at preventing severe illness and hospitalization, the COVID vaccine’s efficacy waned over time, as antibodies naturally do.

Pfizer’s booster study examined more than 10,000 people ages 16 years old and older. The trial found that the vaccine’s efficacy rate was consistent regardless of age, sex, race, ethnicity or comorbid conditions, officials said Thursday.

Participating individuals reportedly received their booster shot, or a placebo, about 11 months after receiving their second dose of the vaccine. During the study, only five people who received a booster shot contracted COVID-19, while 109 individuals who received the placebo contracted the virus.

The study was carried out while the delta variant was the most prevalent COVID strain, officials said.

“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 at 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. We look forward to sharing these data with health authorities and working together to determine how they can be used to support the rollout of booster doses around the world.”

Pfizer’s COVID-19 booster shot was authorized by the Food and Drug Administration in September, but only for older Americans, nursing home residents and individuals who have underlying conditions and are more vulnerable. The Centers for Disease Control and Prevention also endorsed the booster shot, adding people who have risky jobs to the list.

On Wednesday, the FDA signed off on extending COVID-19 boosters to Americans who got the Moderna or Johnson & Johnson vaccine, while also saying that mixing COVID vaccines when receiving a booster shot is OK.

Read more: FDA OKs mixing COVID vaccines; backs Moderna, J&J boosters

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About the Author:

Cassidy Johncox is a senior digital news editor covering stories across the spectrum, with a special focus on politics and community issues.