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# AstraZeneca Covid Vaccine Efficacy Revised to 76%
- URL: https://www.fdaweb.com/astrazeneca-covid-vaccine-efficacy-revised-to-76/
- Published: 2021-03-25T12:00:00.000Z
- Updated: 2026-09-14T16:52:22.000Z
- Author: David McFarland
- Tags: Biologics, #legacy-id-D5148962

AstraZeneca has lowered its Covid-19 clinical trial vaccine efficacy rate from 79% to 76% after conducting a “primary analysis” following a data and safety monitoring board concern that the company may have included outdated information ([see story](https://www.fdaweb.com/astrazeneca-scrutinized-on-covid-vaccine-data/)) in releasing information earlier this week.“ The primary analysis is pre-specified in the protocol and will be the basis for a regulatory submission for Emergency Use Authorization to the U.S. Food and Drug Administration in the coming weeks,” the [company says](https://www.astrazeneca.com/content/astraz/media-centre/press-releases/2021/azd1222-us-phase-iii-primary-analysis-confirms-safety-and-efficacy.html?ref=fdaweb.com). The vaccine also showed 100% efficacy in preventing severe or critical disease and hospitalization, it says, adding that there were eight cases of severe Covid-19 and all were in the placebo group.