The trial of a Chinese-produced coronavirus vaccine under way in Brazil was halted after a participant suffered a "serious adverse event."
The pause was called on Oct. 29, according to a statement posted on the website Brazil's health regulator, the National Health Surveillance Agency (Anvisa).
© Andre PennerButantan Institute Director Dimas Covas, left, and Sao Paulo state Health Secretary Dr. Jean Gorinchteyn, give a press conference about the health regulator Anvisa's decision to halt clinical trials of the experimental coronavirus vaccine CoronaVac in Sao Paulo, Brazil, Tuesday, Nov. 10, 2020.
Butantan Institute Director Dimas Covas, left, and Sao Paulo state Health Secretary Dr. Jean Gorinchteyn, give a press conference about the health regulator Anvisa's decision to halt clinical trials of the experimental coronavirus vaccine CoronaVac in Sao Paulo, Brazil, Tuesday, Nov. 10, 2020. (Andre Penner/)
After learning of the event, Anvisa "decided to interrupt the study to evaluate the data observed so far and judge the risk/benefit of continuing the study," the agency said in a statement, according to CNN.
The agency did not divulge what the event was or cite any other details, citing confidentiality concerns and rules. BBC News reported that the study subject had died. But health officials said the death was unrelated to the vaccine itself.
Phase 3 trials of CoronaVac, the candidate being developed by Chinese drugmaker Sinovac Biotech PLC, have been under way since July in collaboration with the Brazilian Butantan Institute in São Paulo, reported CNN.
The announcement caught the Butantan Institute by surprise, especially given that by all accounts the alleged death was unrelated to the vaccine.
Jean Gorinchteyn, Health Secretary for the state of São Paulo, told reporters Tuesday that the death was an "external event"unrelated to the vaccine, BBC News reported. That echoed similar statements by Dimas Covas, who heads the Butantan Institute, BBC News said.
"We found this Anvisa decision strange, because it is unrelated to the vaccine," Covas told TV Cultura, according to BBC News. "There are more than 10,000 volunteers at this moment."
He added that the institute had not been consulted and had learned about the suspension via the press.
Anvisa president Antonio Barra Torres said Tuesday that the decision was taken because the agency lacked enough details about what had happened to the volunteer.
"We need to receive clear, accurate and complete documents, which did not happen," Torres said, according to The Wall Street Journal.
Halting vaccine trials is not uncommon, as The Associated Press noted. Last month Johnson & Johnson paused its trial after a participant became ill. That study is about to start recruiting again, having determined the illness was unrelated to the vaccine, AP said.
Likewise, in September, the Phase 3 trial for the vaccine being developed at Oxford University and made by AstraZeneca was halted after a participant's adverse reaction.
The Chinese vaccine itself is being turned into something of a political football kicked between President Jair Bolsonaro, who backs another one under development, and São Paulo governor João Doria, who may run for president himself in 2022 and is a proponent of the now-stalled one, The Wall Street Journal reported.
Bolsonaro hailed the halt, BBC News reported, calling it "another victory for Jair Bolsonaro" in a statement posted on Facebook. He's rooting for the Oxford-AstraZeneca version, The Wall Street Journal said, and has already earmarked $350 million to buy 100 million doses once it's deemed ready.
Doria has championed the Sinovac version and promised to try and vaccinate everyone in São Paulo state by March 2021.
As the vaccine drama unfolded, Brazil's health ministry on Tuesday recorded 23,973 new COVID-19 cases and 174 more deaths, for a total of 162,802 - the second-highest in the world, after the U.S.