Janssen-Cilag notified Anvisa that testing to determine the safety and efficacy of its vaccine VAC31518COV3001 "was temporarily suspended due to a serious adverse occurrence in a volunteer abroad."

The company did not provide more details about the case, as the volunteer's health status is kept confidential.

According to Anvisa, the trials will not resume until there is an investigation into the cause of the problem by the Independent Safety Committee, as part of good clinical practice procedures.

"In Brazil, the inclusion of the first volunteer in the study occurred on Oct. 9 and new inclusions can only occur when there is authorization from Anvisa, which will proceed with the analysis of the research data and decide on the continuity or permanent suspension based on the safety and risk/benefit assessment," the agency said.

Janssen-Cilag received authorization from Anvisa in August to carry out the trials in Brazil.