AstraZeneca says revised data shows COVID-19 vaccine 76 percent effective

AstraZeneca said in a press release late Wednesday that a new analysis of its large U.S. clinical trial found its beleaguered COVID-19 vaccine to be 76 percent effective at preventing symptomatic COVID-19 and 100 percent effective at averting severe illness and hospitalization. The new findings, which include 49 more COVID-19 cases from March, lowered the efficacy rate slightly from the 79 percent reported Monday.

The AstraZeneca vaccine, developed by Oxford University researchers, has suffered an unusually rocky rollout. In the most recent drama, the independent monitoring board overusing AstraZeneca's 32,000-volunteer U.S. trial pushed the Anglo-Swedish company to update its analysis based on more recent data, including the National Institute of Allergy and Infectious Diseases in its letter. The NIAID then said in a public statement that AstraZeneca's "outdated information" may have given an "incomplete view of the efficacy data."

"This is really what you call an unforced error, because the fact is this is very likely a very good vaccine," NIAID Director Dr. Anthony Fauci said on Tuesday's Good Morning America.

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The new data includes 190 COVID-19 cases that occurred during the study and 14 possible cases that are still being analyzed, meaning the efficacy rate could still change slightly. Eight people, all of whom received placebos instead of the vaccine, became severely ill. The new data bumped the efficacy rate among vaccine recipients 65 and older up to 85 percent, from 80 percent. AstraZeneca said it will submit its final analysis for peer review in a journal.

"Based on a statistical measure called confidence intervals given in the press release, the end result on overall efficacy could be anywhere between 68 percent and 82 percent — figures that would more than pass the Food and Drug Administration's criteria for an emergency use authorization," Stat News reports. The FDA will decide based on an independent analysis of AstraZeneca's raw data.

Eric Topol, director of the Scripps Research Translational Institute, told Stat the revised results are "better than expected," given the public fight with the monitoring board and NIAID, and he's "relieved since the world needs the vaccine badly." The "3 percentage point difference in efficacy isn't much, but the public relations damage to the vaccine brought on by the last few days may be hard to undo," Caitlin Owens notes at Axios. Several researchers told Stat that after all the twist and turns with AstraZeneca, they will withhold judgment until more results are available.