AstraZeneca issued a statement March 25 saying its COVID-19 vaccine is 76 percent effective in preventing symptomatic cases after its March 22 vaccine efficacy announcement was challenged by the National Institute for Allergy and Infectious Diseases.
AstraZeneca said March 22 its COVID-19 vaccine demonstrated 79 percent efficacy at preventing symptomatic COVID-19 and 100 percent efficacy at preventing severe disease and hospitalization in its U.S. phase 3 trial. Less than a day after, the National Institute for Allergy and Infectious Diseases issued a statement saying the drugmaker's announcement may have been based on outdated data.
NIAID's statement, issued just after midnight on March 23, said that its data and safety monitoring board expressed concern that AstraZeneca's announcement was based on "outdated information from that trial, which may have provided an incomplete view of the efficacy data." The data and safety monitoring board notified AstraZeneca and the Biomedical Advanced Research and Development Authority of its concerns.
In its March 25 statement, AstraZeneca lowered the vaccine's efficacy against symptomatic COVID-19 from 79 percent to 76 percent and maintained that it is 100 percent effective in preventing severe disease and hospitalization.
The drugmaker said its new announcement was based on 190 symptomatic COVID-19 cases that occurred among 32,449 participants in its phase 3 U.S. trial, 49 more cases than disclosed in the March 22 analysis. The new announcement also said the vaccine was 85 percent effective in trial participants ages 65 and older, an increase from the 80 percent efficacy the drugmaker reported for this group March 22.
AstraZeneca said it will apply for FDA emergency approval within weeks. The vaccine is already authorized for emergency use in dozens of countries.
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