AstraZeneca Plc reported a slightly lower efficacy rate for its Covid-19 vaccine after the results of an American clinical trial were criticized as outdated, raising further questions over the controversial shot and whether it will be approved in the U.S.
The company said the shot was 76% effective in its U.S. trial in a statement on Thursday, after an independent monitoring board expressed concern that its previous disclosure of 79% efficacy relied on outdated information. The earlier reading was based on data gathered through Feb. 17.