The coronavirus vaccine developed by AstraZeneca and the University of Oxford provided strong protection against Covid-19 in a large clinical trial in the United States, completely preventing the worst outcomes from the disease while causing no serious side effects, according to results announced on Monday.
The findings, announced in a news release from AstraZeneca, may help shore up global confidence in the vaccine, which was shaken this month when more than a dozen countries, mostly in Europe, temporarily suspended the use of the shot over concerns about possible rare side effects. The trial, involving more than 32,000 participants, was the largest test of its kind for the shot.
The vaccine was 79 percent effective overall in preventing symptomatic infections, higher than observed in previous clinical trials. The trial also showed that the vaccine offered strong protection for older people, who had not been as well-represented in earlier studies. But the fresh data may not make much difference in the United States, where the vaccine is not yet authorized and may not be needed.If AstraZeneca wins authorization for emergency use in the United States based on the new results, the vaccine is unlikely to become available before May, when federal officials predict that three manufacturers that already have authorization will be producing enough doses for all the nation’s adults.AstraZeneca said on Monday that it would continue to analyze the new data and prepare to apply “in the coming weeks” for emergency authorization from the Food and Drug Administration.
It already has approval in more than 70 countries, but clearance from American regulators, if the company can secure it, would bolster the vaccine’s reputation globally. The interim results announced on Monday were based on 141 Covid-19 cases that had turned up in volunteers. Two-thirds of participants were given the vaccine, with doses spaced four weeks apart, and the rest received a saline placebo.
Volunteers were recruited from Chile and Peru as well as the United States.None of the volunteers who got the vaccine developed severe symptoms or had to be hospitalized, a major selling point for the shot. However, AstraZeneca did not disclose how many volunteers had developed severe Covid-19 or had to be hospitalized after receiving the placebo, making it difficult to know how statistically powerful those findings are.