Pfizer asked U.S. regulators to allow boosters of its Covid-19 vaccine for anyone 18 or older, a step that comes amid concern about increased spread of the coronavirus with holiday travel and gatherings.
Older Americans and other groups particularly vulnerable to the virus have had access to a third dose of the Pfizer and BioNTech vaccine since September. But the Food and Drug Administration has said it would move quickly to expand boosters to younger ages if warranted.
Pfizer is submitting early results of a booster study in 10,000 people to make its case that it's time to further expand the booster campaign.
While all three vaccines used in the U.S. continue to offer strong protection against severe Covid-19 illness and death, the shots' effectiveness against milder infection can wane over time.
Pfizer's new study concluded a booster could restore protection against symptomatic infection to nearly 96%, even as the extra-contagious delta variant was surging. Side effects were similar to those seen with the company's first two shots.