AstraZeneca on Wednesday evening released updated information on its COVID-19 clinical trial, showing an effectiveness rate of 76%, down from the 79% rate it claimed earlier in the week.
On Monday, the company, which has developed its vaccine in collaboration with scientists at Oxford University, released interim data from a 32,000-person trial conducted in the U.S., Chile and Peru.
However, an independent review committee that examined the results said the data was misleading, because it contained information only through Feb. 17.
As of Feb. 17, 141 people in the trial had come down with COVID-19, the vast majority in the group that received a salt-water placebo rather than the active vaccine. Among those people, the vaccine was shown to 79% effective in preventing any symptoms of COVID-19 and 100% effective in preventing severe disease and hospitalizations.
The updated information, which included 190 symptomatic cases, showed only a slightly different picture.
The vaccine prevented 76% of cases of symptomatic disease two weeks after the second dose, as well as all severe disease and hospitalizations, according to the updated data. It was 85% effective against symptomatic COVID-19 in trial volunteers aged 65 and over, according to the new data, instead of the 80% reported earlier.
Eight trial participants developed severe COVID-19, all of whom received a saline shot instead of active vaccine, the company said.
Fourteen more cases of possible or probable infection have yet to be fully examined so the figures may change slightly, the company said.
The updated figures show the vaccine remains effective enough to meet the FDA’s standards for effectiveness.