The small revision to the efficacy rate will go a long way to putting the vaccine back on track for gaining U.S. emergency use authorisation – which it plans to seek in the coming weeks – and help AstraZeneca in its efforts to dispel doubts about its effectiveness and side-effects, independent experts said.

AstraZeneca also reiterated that the shot, developed with Oxford University, was 100% effective against severe or critical forms of the disease. There have been eight severe cases – all among trial participants who received the placebo.

“The vaccine efficacy against severe disease, including death, puts the AZ vaccine in the same ballpark as the other vaccines,” said William Schaffner, an infectious disease expert from the Vanderbilt University School of Medicine, adding that he expects the shot to gain U.S. approval.

The latest data was based on 190 infections among more than 32,400 participants in the United States, Chile and Peru. The earlier interim data was based on 141 infections through Feb. 17.