U.S. Health Officials Raise Concerns Over AstraZeneca Vaccine Data

U.S. officials said they were told AstraZeneca AZN -3.83% PLC may have released outdated information about trial results for its Covid-19 vaccine—a surprise disclosure that immediately cast doubt on the company’s assertion a day before that results showed the shot to be highly effective.

The early-morning statement from the National Institute of Allergy and Infectious Diseases came a day after AstraZeneca released interim data from large-scale U.S. trials that it said found its Covid-19 vaccine to be 79% effective in preventing symptomatic disease.

AstraZeneca, in its own statement, said it...