Longer interval between doses boosts CoronaVac efficacy, says Brazilian institute

A COVID-19 patient is transferred in Brasilia, Brazil, on March 25, 2021. (Photo by Lucio Tavora/Xinhua)

SAO PAULO - A new study led by Brazil's biomedical Butantan Institute has shown that China's CoronaVac vaccine can be more effective at protecting against COVID-19 with a longer interval between the two doses.

The study was published on preprints database SSRN and submitted to the medical journal The Lancet on Sunday for peer review.

Data from a subgroup of 12,396 participants shows that the vaccine's efficacy rate grew to 62.3 percent when the doses were given at an interval of 21 days or longer.

"This study corroborates what we had already announced about three months ago and gives us even more confidence about the effective protection provided by the vaccine," Dimas Covas, director of the institute, told Brazil's TV network GloboNews.

The study also shows that CoronaVac is effective against P1, a more contagious variant that emerged in Amazonas in November.

Butantan Institute, a local producer of the CoronaVac vaccine from the Chinese laboratory Sinovac, has supplied doses for Brazil's mass vaccination campaign since Jan 17.