(AP) — Pfizer says its updated COVID-19 booster significantly revved up adults’ virus-fighting antibodies. It released the early findings from a rigorous study of the new shots.

Booster doses tweaked to target the most common omicron strain rolled out in early September, and the Food and Drug Administration said the latest data should spur more Americans to get one.

A month after receiving the new booster, Pfizer says antibody levels in people 55 and older had jumped 13 times higher than before the extra dose.

The results are preliminary, the study is still underway and infection-fighting antibodies naturally wane over time. Still, the FDA had cleared the updated boosters.

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