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Pfizer says Israel data shows third shot restores efficacy to 95%


A third dose of Pfizer‘s Covid vaccine six months after a second shot restores protection from infection to 95% in a real-world setting in Israel, according to data submitted by the company to the Food and Drug Administration.

Pfizer presented 52 pages of data Wednesday to show that while the effectiveness and safety of the mRNA vaccine decreases over time, booster shots can still produce an immune response comparable to the one generated by a second shot.

Pfizer said data from Israel’s Covid vaccination program administering boosters to the entire population show that a third shot “has a reactogenicity profile similar to that seen after receipt of the second primary series dose and restores high levels of protection against Covid-19 outcomes (back to approximately 95% protection).” Data was collected between July 1, and Aug 30, during the spike in the Delta variant.

The FDA published the data because the Biden administration is urging it to issue booster shots as soon as possible. But agency staff declined to take a stance on the need for a third shot, citing the lack of verified data in a 23-page report released later Wednesday.

Staff said they are currently reviewing “potentially relevant studies” on the decline in immunity to Pfizer’s vaccine. However, these studies produced mixed results so some data might be more reliable than other. Although the Israeli data was derived from observational studies, they don’t meet all of the criteria for a clinical trial.

While observational studies may provide insight into real-world effectiveness and can be useful in understanding the impact of these factors on reliability, it is worth noting that there are unknown and well-known biases. The FDA staff explained that some studies might be more reliable than other because of these biases in their analysis.

Pfizer’s report is meant to brief the FDA’s Vaccines and Related Biological Products Advisory Committee, which meets Friday to review the request by Pfizer and its coronavirus vaccine partner, BioNTech, to approve Covid booster doses for the general public. These documents give a look at the FDA’s perspective on third shots.

Based on the data, Pfizer said it “is requesting licensure of a booster dose of [the Pfizer vaccine] administered intramuscularly approximately 6 months after dose 2 in individuals greater than 16 years of age.”

Data from Phase 3, which involved 300 individuals aged 19-55, was also presented by Pfizer. The documents show that one-third of the participants were overweight, and another third were obese.

Pfizer and BioNTech want the U.S. government to allow them to provide booster doses for people aged 16 or older.