AstraZeneca says its vaccine was 79% effective at preventing any COVID-19 symptoms and 100% at preventing severe ones in large-scale U.S. trials, and also had no safety issues with blood clots.
The results of the trials involving 32,449 people, reported Monday, pave the way for the company to request emergency-use authorization in the U.S.
Notably, the company said the vaccine was 80% effective in people 65 and older. Its efficacy was also consistent across ethnicities.
"These findings re-confirm previous results observed in ... trials across all adult populations, but it's exciting to see similar efficacy results in people over 65 for the first time," Ann Falsey, a professor at the University of Rochester School of Medicine in New York and the co-lead principal investigator for the trial, said. "This analysis validates the AstraZeneca COVID-19 vaccine as a much-needed additional vaccination option."
In the trials, 21,583 participants received two doses of the vaccine four weeks apart. The rest of the test volunteers were injected with a placebo. Out of the entire pool of participants, 141 people developed COVID-19 symptoms, the company said.
The new data come after several countries, including Germany and France, halted use of the shots earlier this month because of reports of fatal blood clots in a very small number of recipients on the European mainland. The company said that, with the help of an independent neurologist, it specifically examined the U.S. trial data for information regarding blood clots, or thrombosis, and found no safety concerns.
"The vaccine was well-tolerated, and the independent data safety monitoring board (DSMB) identified no safety concerns related to the vaccine," the company said in a statement, adding: "The DSMB found no increased risk of thrombosis or events characterized by thrombosis among the 21,583 participants receiving at least one dose of the vaccine."
The European Union's drugs regulator said last week that there was no evidence linking the vaccine with an overall increased risk of blood clots, although it could not definitively rule out an association between the shot and the reported incidents. Blood clots were reported in at least 37 people among the 17 million EU residents who have received one or more doses of the AstraZeneca vaccine. Four of those cases turned out to be fatal, but the European Medicines Agency said the benefits of getting inoculated far outweighed any potential risks.
"If it were me, I would be vaccinated tomorrow," agency chief Emer Cooke said Thursday.
Germany, Indonesia and other countries began resuming use of the AstraZeneca shot a day later. But snap polls have shown a drop in public confidence in the vaccine in some European nations, adding another challenge to the European Union's vaccine rollout, which has been heavily criticized for its slowness.
AstraZeneca said the U.S. trial results reported Monday showed anew that its vaccine was safe and effective.
"We are confident this vaccine can play an important role in protecting millions of people worldwide against this lethal virus," senior AstraZeneca executive Mene Pangalos said. "We are preparing to submit these findings to the U.S. Food and Drug Administration and for the rollout of millions of doses across America should the vaccine be granted U.S. emergency-use authorization."
