AstraZeneca’s U.S. trial shows coronavirus vaccine is 79 percent effective

Oxford University and AstraZeneca reported on Monday that their coronavirus "vaccine for the world" was safe and 79 percent effective overall, according to data from a long-awaited clinical trial in the United States, alongside other studies in Chile and Peru. The two-shot regimen was completely effective at preventing severe cases of illness.

In a news release, the Oxford researchers, who developed the easily transported $4 shot for the British-Swedish pharmaceutical giant AstraZeneca, said their coronavirus vaccine is “safe and highly effective, adding to previous trial data from the United Kingdom, Brazil and South Africa, as well as real-world impact data from the United Kingdom.”

An independent monitoring board combed through the data to look for any cases of blood clotting events similar to those that caused the vaccination effort to be suspended in many European countries. While vaccination was started again after a pause, it undermined confidence in the vaccine. The independent board found no suggestion that the vaccine carried an increased risk of clotting.

The trials included 32,449 adult participants in all age groups, most of them in the United States. The volunteers received either two standard doses of the Oxford-AstraZeneca vaccine or a placebo, at a four-week interval, the researchers said.

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The scientists said the data show the vaccine is 79 percent effective against symptomatic covid-19, the disease caused by the coronavirus, and 100 percent effective against severe illness. There were five cases of severe illness in the trial, all of them in the group that received a placebo.

“The data look good. The numbers don’t lie,” said Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases, who said he was briefed on the data on Sunday.