A volunteer in a clinical trial of the coronavirus vaccine developed by AstraZeneca has died, Brazil's National Health Surveillance Agency (ANVISA) confirmed on Wednesday.
The British-Swedish multinational is developing the vaccine in cooperation with Oxford University.
CNN Brazil reported that the volunteer was a 28-year-old man from Rio de Janeiro and that he died from complications related to Covid-19, the disease caused by the coronavirus.
But the newspaper O Globo said he had received a placebo instead of the vaccine, quoting unnamed sources.
Tests were due to continue while the case was being evaluated.
In September, AstraZeneca temporarily paused trials of the vaccine after a participant fell ill.
Brazil has confirmed more than 5.2 million coronavirus infections, the third-highest number worldwide.