AstraZeneca Pharmaceutical Company said its COVID-19 vaccine was 76 percent effective in a new analysis of its trial in the United States - only a bit lower than the level in an earlier report this week criticized for using outdated data.

Interim data published on March 22 had put the vaccine's efficacy rate at 79 percent but had not included more recent infections, leading to a highly unusual public rebuke from U.S health officials.

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 percent 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.

It also said the vaccine showed 85 percent efficacy in adults 65 years and older, higher than the 80 percent rate reported on Monday. AstraZeneca said the latest data has been presented to the independent trial oversight committee, the Data Safety Monitoring Board, and it plans to submit the analysis for peer-reviewed publication in the coming weeks.

The updated 76 percent efficacy rate compares with rates of about 95 percent for vaccines from Pfizer/BioNTech and Moderna in their trial data. Experts have noted, however, that AstraZeneca's latest data is particularly significant because it was compiled after more infectious variants of the coronavirus became prevalent.

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