LONDON—U.S. officials said they were told AstraZeneca PLC may have released outdated information about trial results for its Covid-19 vaccine—a surprise disclosure that immediately cast doubt on the company’s assertion a day before that results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.
The results served as a vote of confidence in the shot, which has been clouded by uncertainty over previous, confusing efficacy results and large-scale production problems. More recently, reported cases of rare blood clotting in Europe raised concerns about the vaccine’s safety, though European regulators have recommended its continued use. The U.S. trials showed no link with the vaccine and the NIAID statement Tuesday didn’t raise questions about that finding.
NIAID, in its highly unusual statement, said an independent data monitoring board working with AstraZeneca in conducting its trials raised concerns about the company’s disclosures and had urged the drugmaker to work with it to ensure that the most accurate, up-to-date efficacy data would be made public.
NIAID said the monitoring board, an independent body that works alongside a drug company to conduct trials, “expressed concern that AstraZeneca may have included outdated information from that trial.” It said that could have “provided an incomplete view of the efficacy data.” The agency said it was urging AstraZeneca “to review the efficacy data and ensure the most accurate, up-to-date efficacy data be made public as quickly as possible.”