Brazilian health officials suspended clinical trials of China’s Sinovac coronavirus vaccine on Monday following a “severe adverse event” involving a volunteer recipient, according to multiple reports.
The nation's health regulator, Anvisa, announced that the event occurred on Oct. 29, although it did not immediately provide additional details.
Brazil’s Butantan Institute, a research center that has been developing the vaccine alongside Sinovac, said it was surprised by the move, The Wall Street Journal reported.
The director of the institute, Dimas Covas, said one volunteer had died, but the death was not related to the vaccine trials, the Journal noted.
Sinovac on Tuesday also said it remains confident in the safety of its potential vaccine and that it has not found adverse reactions or cases in other ongoing trials. Trials for the vaccine are also ongoing in Indonesia and Turkey, the BBC reported.
The Chinese drugmaker began phase three trials of its vaccine in collaboration with the Butantan Institute in July.
Drugmaker AstraZeneca paused trials of its coronavirus vaccine in September to investigate a “potentially unexplained illness” in a participant. However, global phase three trials for the COVID-19 vaccine have since continued.
Brazil has been one of the hardest-hit countries in the world amid the ongoing coronavirus pandemic. The country has documented over 5.6 million total COVID-19 cases, as well as over 162,000 fatalities.
Brazil has the third-highest total number of cases, following only the United States and India. It has the second-highest number of fatalities worldwide, after the U.S.
The news comes as an interim analysis showed Pfizer's vaccine candidate was more than 90 percent effective in preventing the disease, which is caused by the novel coronavirus.