(Bloomberg) -- Pfizer Inc. said that data from the U.S. and Israel suggest that the efficacy of its Covid-19 vaccine wanes over time, and that a booster dose was safe and effective at warding off the virus and new variants.

The company detailed the data in a presentation it will deliver to a meeting of outside advisers to the Food and Drug Administration on Friday. 

The panel is expected to make recommendations for whether more Americans should receive booster shots.

“Real-world data from Israel and the United States suggest that rates of breakthrough infections are rising faster in individuals who were vaccinated earlier,” Pfizer said in its presentation, which was posted on the FDA website.

The decrease in effectiveness is “primarily due to waning of vaccine immune responses over time,” rather than the delta variant, Pfizer researchers said in the presentation.

According to a meeting agenda the FDA posted on its website, in addition to the Pfizer presentation, the Friday panel will include presentations from the Centers for Disease Control and Prevention, FDA staff and researchers from Israel and the U.K.

The Israel officials will present data from that country on booster protection against infections and severe disease, according to the agenda, while a professor of medical statistics from the University of Bristol will present data on real-world vaccine effectiveness.

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