Brazil's health regulator has suspended trials of a Chinese-developed Covid-19 vaccine following a "serious adverse event" involving a volunteer recipient, according to sources cited by CNN's affiliate, CNN Brasil.
Chinese drugmaker Sinovac Biotech began Phase 3 trials of its CoronaVac in collaboration with the Brazilian Butantan Institute in Sao Paulo in late July, with an aim to recruit 130,000 volunteers. Phase 3 trials represent the final and most important testing stage before regulatory approval is sought.
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.
According to a note from Brazil's National Health Surveillance Agency, an incident reported on October 29 led to a decision to suspend the trial in order to better evaluate the data and assess the risk.
"With the study interrupted, no new volunteers can be vaccinated," read the note published by CNN Brasil late Monday.