AstraZeneca releases updated trial results for COVID-19 vaccine

March 25, 2021

AstraZeneca late Wednesday released results of its primary analysis of the U.S. Phase III trial for its COVID-19 vaccine, which it says confirms the interim results released Monday, according to a company news release.

The results of the updated analysis showed that the vaccine was 75% effective at preventing symptomatic COVID-19, occurring 15 days or more after receiving two doses given four weeks apart. In addition, the company said the results were comparable across age groups, with vaccine efficacy of 85% in adults 65 years and older. A key secondary endpoint, preventing severe or critical disease and hospitalization, demonstrated 100% efficacy. There were eight cases of severe COVID-19 observed in the primary analysis with all of those cases in the placebo group.

AstraZeneca was responding to a statement from the National Institute of Allergy and Infectious Diseases (NIAID) at the National institutes of Health (NIH). In the statement, NIAID said the Data and Safety Monitoring Board raised questions about the interim data AstraZeneca released Monday, saying the company “may have included outdated information from that trial, which may have provided an incomplete view of the efficacy data.”

AstraZeneca said the updated results have been presented to the independent Data Safety Monitoring Board, and will be the information it will submit in the coming weeks to the U.S. Food and Drug Administration (FDA) for emergency use authorization (EUA).

This primary efficacy analysis included the accrual of 190 symptomatic cases of COVID-19 from the 32,449 trial participants, adding an additional 49 cases to the previously announced interim analysis. Participants were randomized on a 2:1 ratio between the vaccine and placebo group.

There are 14 additional possible or probable cases to be adjudicated, so the total number of cases and the point estimate may fluctuate slightly, AstraZeneca said.

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