China’s CoronaVac is showing mere 50.4 percent efficacy in late-stage trials taking place in Brazil — far lower than earlier projections and barely enough to gain regulatory approval.
The new data, reported by researchers on Tuesday, is a big blow to the South American country as it weathers a second wave of one of the largest COVID-19 outbreaks worldwide.
The Beijing-made inoculation from Sinovac is just one of two vaccines that have been approved for trials by Brazilian authorities, the outlet reported.
Last week, researchers in Brazil celebrated results showing a much higher efficacy rate of 78 percent against “mild to severe” COVID-19 cases, but didn’t disclose there was a group of people who received the vaccine and still developed “very mild” infections.
The latest data includes that group, according to Richard Palacios, medical director for clinical research at Sao Paulo’s Butantan biomedical center.
Palacios and government officials insisted the data was still good news, because none of the volunteers required hospitalization — so even if the vaccine is effective only 50 percent of the time, the cases are mild and won’t further strain the country’s overloaded hospitals.
“It’s a vaccine that will start the process of overcoming the pandemic,” microbiologist Natalia Pasternak told Reuters.
“We have a good vaccine. Not the best vaccine in the world. Not the ideal vaccine,” the scientist said, criticizing Butantan’s triumphant tone.
Butantan officials also argued the design of Brazil’s study — which focused on front-line health workers and used elderly volunteers — made it impossible to compare to other trials happening outside the country.
Turkish researchers found last month the Beijing-made inoculation was 91.25 percent effective and Indonesia just granted the vaccine emergency approval on Monday when interim data showed it to be 65 percent effective.
Pfizer and Moderna’s shots, both of which have been approved for emergency use in the US, have each been shown to be 95 percent effective in warding off COVID-19 in their crucial Phase 4 trials.
Brazil’s national immunization program is banking on CoronaVac, along with the shot created by Oxford University and AstraZeneca. Neither have been approved for use.