Home / Science / Health /  Pfizer-BioNTech Covid-19 booster shot was 95.6% effective in large trial, companies say

A third dose of the Covid-19 vaccine from Pfizer Inc. and BioNTech SE was found in a large study to be highly protective against symptomatic Covid-19, the companies said Thursday.

Researchers found 109 cases of symptomatic Covid-19 among study subjects who received a placebo shot, compared with five cases in people who took the vaccine, resulting in 95.6% efficacy, the companies said.

The additional dose was safe and tolerable, and consistent with what was known about the vaccine, the companies said.

The study was carried out while the highly contagious Delta variant was prevalent, the companies said, suggesting the booster helps protect against the contagious strain.

“These results provide further evidence of the benefits of boosters as we aim to keep people well-protected against this disease," said Albert Bourla, Pfizer Chief Executive Officer.

The results were the first from a study testing whether an additional dose of a Covid-19 vaccine provides protection in people. Up until now, companies have reported a booster increased antibody levels but not tied the immune response specifically to whether that meant increased protection.

Based on the antibody data, U.S. health authorities in September authorized a third dose of the Pfizer-BioNTech vaccine for adults 65 years and older and others at high risk.

The data could help the U.S. Food and Drug Administration as it weighs whether to broaden Pfizer’s booster use beyond the seniors and high-risk people permitted under current authorization.

The companies said they planned to submit the data to health authorities in the U.S. and other countries.

The companies reported the findings in a press release and provided few medical details. The results haven’t been published in a peer-reviewed medical journal.

“Based on these findings we believe that, in addition to broad global access to vaccines for everyone, booster vaccinations could play an important role in sustaining pandemic containment and a return to normalcy," said BioNTech CEO Ugur Sahin.

In the study, the companies enrolled more than 10,000 people who were 16 years and older and had received the two-dose shot. Pfizer and BioNTech enrolled subjects in the U.S., Brazil and South Africa who had been part of the late-stage study that led to the vaccine’s original authorization. Half of the subjects got a booster dose, and the rest took a placebo.

On average, the people received a booster dose 11 months after their second dose.

The protection from the vaccine was consistent across age, sex, race, ethnicity and comorbidities, the companies said, although they didn’t provide any details.

About half of the subjects were between 16 and 55 years, while nearly one-quarter of the subjects were 65 years and older.

The companies had announced that a third dose generated a stronger immune system against the original Covid-19 strain compared with the original two-dose course.

As part of its application for booster authorization in September, Pfizer and BioNTech had provided health regulators antibody data of the vaccine against the Delta variant in a small number of subjects.

Booster doses for vaccines from Johnson & Johnson and Moderna Inc. were cleared by the FDA this week, as well as mixing and matching vaccines and the extra doses.

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