British pharmaceutical firm AstraZeneca has updated analysis of its coronavirus vaccine's clinical trial data. It says the vaccine's efficacy was 76 percent, 3 points lower than the figure announced earlier this week.
AstraZeneca's release of the information on Thursday comes after its report on Monday raised accuracy questions.
The National Institute of Allergy and Infectious Diseases in the US said the interim analysis may have included outdated information, which "may have provided an incomplete view of the efficacy data."
AstraZeneca says the earlier analysis was based on data collected in the US and elsewhere through February 17.
It says the latest report was based on 190 cases of infections, 49 more than in the interim analysis.
The latest analysis says the AstraZeneca vaccine, developed with the University of Oxford, was 76 percent effective in preventing symptomatic COVID-19. The figure was 79 percent in the previous report.
But it says vaccine efficacy in adults 65 years and older was 85 percent in the new data, up 5 points from the earlier report.
The White House senior advisor for COVID response, Andy Slavitt, said on Wednesday that transparency and trust are important.
But he brushed aside concerns, saying vaccines need to go through screenings by US regulators before being approved for use.