CoronaVac was 66% effective in preventing Covid-19 among fully vaccinated adults, versus 93% for the jab made by Pfizer and its partner BioNTech SE.
The inactivated inoculation, given to more than 10 million Chileans, was slightly less effective in preventing hospitalization and deaths than the mRNA vaccine, which was administered to fewer than half a million people, according to the study, published Wednesday in the New England Journal of Medicine.
The research was conducted from February through May, when the alpha and gamma strains of the virus were the variants of concern most frequently detected in Chile.
Preliminary data released in April found CoronaVac was 67% effective in preventing symptomatic Covid-19 infections and warded off