AstraZeneca says its COVID-19 vaccine is 79 percent effective in large U.S. trial

The AZ/Oxford vaccine
(Image credit: Leon Neal/Getty Images)

AstraZeneca and Oxford University said Monday that their COVID-19 vaccine proved to be 79 percent effective against symptomatic illness and 100 percent effective at preventing serious COVID-19 cases or hospitalization in a U.S. trial involving more than 30,000 people. The vaccine, tested on 32,559 people 18 and older was effective among all age groups and demographics, including 80 percent effective with participants 65 and older.

The U.S. trial's independent safety monitors, aided by an outside neurologist, specifically reviewed the trail data for increased risk of severe blood clotting, following reports of vaccinated people in Europe suffering from cerebral venous sinus thrombosis. The review found no increased risk of thrombosis in the 21,583 volunteers who received at least one dose of the vaccine; the other participants were given a placebo.

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Peter Weber, The Week US

Peter has worked as a news and culture writer and editor at The Week since the site's launch in 2008. He covers politics, world affairs, religion and cultural currents. His journalism career began as a copy editor at a financial newswire and has included editorial positions at The New York Times Magazine, Facts on File, and Oregon State University.