Brazil’s National Health Surveillance Agency (Anvisa) has suspended phase 3 clinical trials of a Chinese-developed Covid-19 vaccine following an "adverse" incident involving a volunteer recipient, according to sources cited by CNN’s affiliate, CNN Brasil.
CoronaVac, developed by Chinese pharmaceutical company Sinovac Biotech, began phase 3 trials of CoronaVac in collaboration with the Brazilian Butantan Institute in Sao Paulo in late July.
According to CNN Brasil, the studies were suspended due to the "occurrence of serious adverse event in one of the volunteers in Brazil." No further details were provided owing to privacy regulations.
The pause in testing marks a potential setback for one of China's leading vaccine candidates and comes as US drugmaker Pfizer said Monday that early data from its own coronavirus vaccine showed more than 90% effectiveness.
In a note obtained by CNN Brasil, Anvisa mentions a case on October 29 for which the agency “determined the interruption of the clinical study,” adding that it “decided to interrupt the study to evaluate the data observed so far and judge on the risk/benefit of continuing the study.”
“With the study interrupted, no new volunteers can be vaccinated,” reads the Anvisa note published by CNN Brasil late Monday.
The CoronaVac trial vaccine uses inactivated virus cells to stimulate an immune response in patients. Testing began in late July, with 9,000 volunteers in five Brazilian states plus the capital.
The Butantan Institute said it will hold a press conference Tuesday morning local time, according to CNN Brasil.