WEDNESDAY, March 16, 2022 (HealthDay News) — Pfizer Inc. said Tuesday that it has asked the U.S. Food and Drug Administration to approve the emergency use of a second COVID-19 booster shot for Americans 65 and older.

In a statement announcing its request, Pfizer relied on data from two studies out of Israel that have been published without peer review on preprint servers.

The first study, conducted in concert with Israel’s Ministry of Health, reviewed the health records of 1.1 million people and concluded that they were less likely to become infected or develop severe illness after a fourth dose of Pfizer’s vaccine. However, Israel only recently began its second booster program, so it was unclear how long the extra protection might last. Israel began offering fourth doses to health care workers in late December, then quickly broadened eligibility to those 60 and older and other vulnerable groups.

The second study, of Israeli health care workers, showed that while fourth shots of either Pfizer’s or Moderna’s vaccine boosted antibody levels, it was not very effective at preventing infections. Researchers said those findings underscored the urgency of developing vaccines that target whatever variant is circulating.

Still, “both data sets showed evidence that an additional mRNA booster increases immunogenicity and lowers rates of confirmed infections and severe illness,” the company said in its statement. Pfizer CEO Albert Bourla, M.D., has said more than once in the past week that the company believes a fourth shot will be needed to counter the waning power of the third shot.

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