LONDON — AstraZeneca’s COVID-19 vaccine provided substantial protection against sickness and eliminated hospitalizations and deaths from the disease across all age groups in a late-stage study in the United States, the company announced Monday.
AstraZeneca said its experts did not identify any safety concerns related to the vaccine, including finding no increased risk of rare blood clots identified in Europe.
Although AstraZeneca’s vaccine has been authorized in more than 50 countries, it has not yet been given the green light in the U.S. — and has struggled to gain public trust amid a troubled rollout. The study comprised more than 30,000 volunteers, of whom two-thirds were given the vaccine while the rest got dummy shots.
In a statement, AstraZeneca said its COVID-19 vaccine was 79% effective at preventing symptomatic COVID-19 and was 100% effective in stopping severe disease and hospitalization, though it has not yet published complete data. Investigators said the vaccine worked across all ages, including older people — something experts wanted better data on. Two doses of the AstraZeneca vaccine were given to people four weeks apart.
“These findings reconfirm previous results observed,” said Ann Falsey of the University of Rochester School of Medicine, who helped lead the trial. “It’s exciting to see similar efficacy results in people over 65 for the first time.”
Dr. Paul Hunter, a professor of medicine at the University of East Anglia, said the results were reassuring but needed more details to back up AstraZeneca’s claim that the vaccine was completely effective at preventing severe disease and hospitalization.
” It would be good to know how many severe cases occurred in the control group and so what the confidence intervals are for this 100% figure,” said Hunter, who was not connected to the study. “But this should add confidence that the vaccine is doing what it is most needed for.”
The early findings from the U.S. study are just one set of information AstraZeneca must submit to the Food and Drug Administration. An FDA advisory committee will publicly debate the evidence behind the shots before the agency decides whether to allow emergency vaccine use. In the past, the time between a company revealing efficacy data and a photo being authorized in the U.S. has been about a month.
Stephen Evans of the London School of Hygiene & Tropical Medicine said the new data is essential for two reasons: The findings will reassure the FDA, which is reluctant to rely on data obtained outside the United States, but they could also boost confidence more broadly in the shot.
“The benefits of these results will mainly be for the rest of the world where confidence in the AZ (AstraZeneca) vaccine has been eroded, largely by political and media comment,” he said.
Scientists had hoped the U.S. study would clear up some of the confusion about just how well the shots really work, particularly in older people. Previous research suggested the vaccine was effective in younger populations, but no reliable data proved its efficacy in those over 65, often those most vulnerable to COVID-19.