Brazil resumes CoronaVac trial after pause over 'adverse event'

According to a police report, a volunteer in the study died by suicide, CNN confirmed Tuesday, resulting in an investigation into the cause of death and a pending toxicology report.

Brazil's National Health Surveillance Agency (Anvisa) said on Wednesday that clinical trials of CoronaVac, developed by Chinese drug maker Sinovac, would be allowed to restart.

Phase 3 of the trials have been suspended since Monday, following what Anvisa described as a "serious adverse event" on October 29. A note from Anvisa said the trial had been paused in order to better evaluate the data and assess the risk.

"After evaluating the new data presented by the sponsor after the study was suspended, Anvisa concludes that there are sufficient benefits to allow the vaccination to resume and continues to monitor the investigation of the outcome of the case to define the possible causal relationship between the unexpected adverse event and the vaccine," Anvisa said in a statement on Wednesday.

"It is important to clarify that a suspension does not necessarily mean that the product under investigation is not of quality, safety or efficacy," it said.

Dimas Covas, the director of Brazil's Butantan biomedical institute, said the incident was not linked to the vaccine trial itself. "The serious adverse event observed in a volunteer in the trial has no relation to the vaccine," Covas told reporters Tuesday at a news conference in Sao Paulo. "It was analyzed and determined that there was no relation."

In a statement posted online Tuesday, Sinovac said it was "confident in the safety of the vaccine."

"We have communicated with our Brazilian partner, the Butantan Institute, and the head of the institute believes the incident has nothing to do with the vaccine. Sinovac will continue to communicate with the Brazilian side on this matter. Work related to our clinical research in Brazil will continue to be carried out in strict accordance with GCP (Good Clinical Practice) requirements," the statement said.

Sinovac began Phase 3 clinical trials of its CoronaVac vaccine in collaboration with the Butantan Institute and the state of 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.

Sinovac is also conducting Phase 3 trials in Indonesia and Turkey. Sinovac did not immediately responded to CNN's request for further comment.

Pausing a clinical trial is not unusual. In September, drug giant AstraZeneca paused global trials of its coronavirus vaccine because of an unexplained illness in one of the volunteers.