AstraZeneca’s COVID-19 vaccine showed 74% efficacy in the prevention of symptomatic disease, a figure that rose to 83.5% in people aged 65 and older, according to long-awaited results from the company’s US clinical trial published on Wednesday.
The overall effect of 74% was lower than the provisional figure of 79% reported by the UK drug manufacturer in March, a result AstraZeneca revised days later to 76% after a rare public reprimand from health officials that the figure was based on ” obsolete information. “
The data looked at more than 26,000 volunteers in the United States, Chile and Peru who received two doses of the vaccine at approximately one-month intervals. The results were published in the New England Journal of Medicine.
There were no cases of severe or critically symptomatic COVID-19 among the more than 17,600 participants who received the vaccine, compared with 8 such cases among the 8,500 volunteers who received placebo. There were also two deaths in the placebo group, but none among those who received the vaccine.
“I was pleasantly surprised,” said Dr. Anna Durbin, a vaccine researcher at Johns Hopkins University and one of the study’s investigators, on the overall result. “It was also extremely protective against serious illness and hospitalization,” she said.
There was no case of a rare but serious side effect of blood clots called thrombosis with thrombocytopenia that has been linked to the AstraZeneca vaccine developed by researchers at Oxford University.
AstraZeneca said in late July that it planned to seek full approval from the U.S. Food and Drug Administration, rather than seek permission for emergency use. CEO Pascal Soriot told a media briefing at the time that he hoped the vaccine could still play a role in the United States, even though the process took longer than expected.
The company is investigating booster doses for people who have already been vaccinated with two doses of either its own or mRNA-based vaccines from Pfizer / BioNTech or Moderna.
The vaccine, known as Vaxzevria, is approved for use in more than 170 countries. A spokesman said the company expects to apply for U.S. approval later this year.
Durbin said she does not expect Vaxzevria to be widely used in the United States, but securing FDA approval “gives them gravity.”