Brazil halts testing of China-developed, possible COVID-19 vaccine, citing 'adverse, serious event'

Brazil has stopped clinical trials on an experimental coronavirus vaccine developed by a Chinese biopharmaceutical firm – following what Brazilian officials described as an “adverse, serious event.”

The announcement was posted Monday night on an official Brazil government website.

The virus, which has been attributed to more than 1.2 million deaths so far, started in China. Brazil has worldwide the third-highest number of virus cases and the second-highest number of virus-related deaths.

The potential vaccine is being developed by Chinese biopharmaceutical firm Sinovac and in Brazil would be mostly produced by Sao Paulo’s state-run Butantan Institute, according to the Associated Press.

Butantan said it was surprised by the decision by the country’s National Health Surveillance Agency and plans to hold a news conference Tuesday on the matter.

The CoronaVac shot has stirred controversy in Brazil, where President Jair Bolsonaro has cast doubt on its prospective effectiveness. He has publicly rejected it, saying Brazilians would not be used as guinea pigs and that he is mistrustful  of China, which appears to have tried to stop the spread of the virus in late-2019 or early-2020 before publicly announcing the problem.

Temporary halts of drug and vaccine testing are relatively common. In research involving thousands of participants, some are likely to fall ill. Pausing a study allows researchers to investigate whether an illness is a side effect or a coincidence. Last month, two drugmakers resumed testing of their prospective coronavirus vaccines in the U.S. after they were halted earlier.