Pfizer Says Third Booster Shot Restores 95% Efficacy For Its COVID Vaccine

By Bill Galluccio

September 15, 2021

Spain Offers Covid-19 Booster To Immunosuppressed
Photo: Getty Images

The Food and Drug Administration has released data provided by Pfizer during its application for approval of a booster shot for its COVID vaccine. The data showed the efficacy of the mRNA vaccine wanes over time and that a booster shot delivered six months after the dose restores the effectiveness to 95%.

The study was conducted in Israel from July 1 through August 30, when the Delta variant was the dominant strain in the country.

After reviewing the data, the FDA did not take a formal stance on the need for a third dose, citing a lack of verified data from Pfizer. They noted that one of the studies provided was from an observational study and not a clinical trial. They also pointed to the mixed results of other studies looking into the long-term immune response of the vaccine.

"It should be recognized that while observational studies can enable understanding of real-world effectiveness, there are known and unknown biases that can affect their reliability. Due to these biases, some studies may be more reliable than others," the FDA wrote in a 23-page analysis of Pfizer's data.

In August, the FDA authorized booster shots for some immunocompromised individuals.

The FDA's Vaccines and Related Biological Products Advisory Committee is scheduled to meet this Friday (September 17) to discuss whether a booster shot is necessary. The agency has been under pressure from the Biden administration, which wants to start distributing booster shots by September 20.

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