Brazil's health officials halted a clinical test of China's Sinovac COVID vaccine because of a serious adverse reaction that caused the death of a patient.

Brazilian President Jair Bolsonaro has repeatedly disapproved of the vaccine because of safety and in October denounced it saying the people of Brazil would not be used as lab rats.

Officials in Sao Paulo, where the clinical trials are being conducted, said the death of a trial volunteer had been confirmed as suicide and authorities are investigating, Reuters reported. With the suspension of the tests, no new volunteers can be immunized, according to a statement by Brazil's health regulator Anvisa.

Anvisa did not give any indication of how long the suspension might last, adding it needed more information. The regulator junked any proposition the move was politically motivated and said it was technical.

Dimas Covas, director of Sao Paulo's medical research institute Butantan Institute, told local television Cultura that a death had occurred but that it had nothing to do with the vaccine, Reuters reported.

The trial's organizers criticized the decision made by Anvisa, saying they were not informed in advance and that there was no reason to halt the test. CoronaVac is being tested in seven states in Brazil.

Sao Paulo Health Secretary Jean Gorinchteyn said the vaccine was safe and that they had an "external event that led to the regulator being notified," Reuters quoted the official as saying.

Brazil has 5.7 million COVID cases with more than 5 million recoveries and 163 deaths. Worldwide, the pandemic has claimed 1.27 million lives with 51.5 million infections and 33.6 million recoveries.

In a statement, Sinovac said its vaccine was not the cause of the death. "We learned the director of Butantan Institute believed that this serious adverse event is not linked to the vaccine," it said.