AstraZeneca said its Covid-19 vaccine was 76 percent effective at preventing symptomatic illness in a new analysis of its major US trial - a tad lower than the level announced earlier this week in a report that was criticised for using outdated information.

US health officials had publicly rebuked the drugmaker for not using the most up-to-date information when it published an interim analysis on Monday that said the vaccine was 79 percent effective...