AstraZeneca says its COVID-19 vaccine was 74 percent effective in US testing

British drugmaker AstraZeneca’s COVID-19 vaccine Vaxzevria has been found to have a 74 percent efficacy in preventing symptomatic disease, according to a report published Wednesday in the New England Journal of Medicine. 

The report, which studied more than 26,000 volunteers in the United States, Chile and Peru, also found the vaccine had an 83.5 percent efficacy rate in people ages 65 and older.

The AstraZeneca vaccine has not been approved for use in the United States, though it has been exported from the U.S. for use abroad.

Vaxzevria is currently authorized in more than 170 countries, with the company seeking U.S. approval later this year. 

In July, AstraZeneca looked to get U.S. approval from the Food and Drug Administration rather than receive emergency authorization, according to The Associated Press.

The 74 percent efficacy rate was lower than the initial 79 percent reported by AstraZeneca in March, which was later revised to 76 percent after health officials said the figure was based on “outdated information.”

There were no severe or critical symptomatic cases of COVID-19 in the more than 17,600 participants who tested positive, compared with eight severe cases among the 8,500 volunteers who received the placebo. The placebo also saw two deaths, but not among those who received the vaccine.

“I was pleasantly surprised,” Anna Durbin, a vaccine researcher at Johns Hopkins University and one of the study’s investigators, told Reuters. “It was also highly protective against severe disease and hospitalization.”

While blood clots were one of the first serious side effects of the vaccine, there were no cases of them in the study group.

The company is still exploring the need for booster doses on those who have already been vaccinated from either its own shot or other mRNA-based vaccines like Pfizer and Moderna, Reuters noted.