Brazil halted a late-stage trial of a Chinese vaccine on Monday that had been considered a global front-runner in the race to develop a protective shot for the coronavirus, after a “serious adverse” reaction in a participant.
The decision provoked a political firestorm on Tuesday after President Jair Bolsonaro, who has been critical of China and spoken dismissively of its vaccine, CoronaVac, called the suspension a political victory.
Instituto Butantan, the Brazilian institute assisting with the CoronaVac trial, called the suspension unwarranted, arguing that it had been triggered by the death of a trial participant, but that the death was unrelated to the vaccine.
Read | Brazil suspends trials of China's Sinovac Covid-19 vaccine due to 'adverse effect'
A police report obtained by The New York Times says the participant’s death, which occurred Oct. 29, is being investigated as a suicide. A senior government official for the State of São Paulo, which runs Instituto Butantan, said that fact led health experts at the institute to conclude that it did not raise red flags about the safety of the vaccine.
São Paulo state, the largest in Brazil, is led by Gov. João Doria, a political rival of Bolsonaro who has criticized the president’s cavalier handling of the pandemic.
Gustavo Mendes, director of pharmaceuticals at Anvisa, Brazil’s health regulatory agency, said in an interview Tuesday that regulators have yet to conclude that the volunteer’s death was unrelated to the vaccine.
“It was a precautionary measure,” he said. “Unfortunately, it’s being politicized.” He added: “Halting a study until there is more information is what is expected of a regulatory agency.”
CoronaVac, which is being developed by the Chinese company Sinovac, is one of 11 experimental vaccines currently in Phase 3 trials.
Sinovac’s drug was seen in China as a leading candidate. But in Beijing’s push to get a Chinese vaccine to be the first on the global market, officials stretched the definition of “emergency use.” They have permitted tens of thousands of people to receive the Sinovac vaccine and two other locally made vaccines, despite having not yet concluded Phase 3 trials.
Adverse effects are not unusual in Phase 3 trials. AstraZeneca and Johnson & Johnson both paused their trials after several volunteers fell seriously ill.
In a statement issued Tuesday, Sinovac said Instituto Butantan had deemed the “serious event” not related to the vaccine. The company said it was “confident in the safety” of its vaccine.