RIO DE JANEIRO — A Brazilian who participated in the clinical trial of an experimental coronavirus vaccine has died, officials here said Wednesday.

Brazil’s National Health Surveillance Agency, which is overseeing multiple vaccine trials in a country suffering one of the world’s worst outbreaks, said the individual volunteered to receive the vaccine candidate developed by Oxford University and produced by AstraZeneca.

The Brazilian newspaper O Globo, citing unnamed sources, reported that the volunteer was in a control group that did not receive the experimental vaccine and died of covid-19. The news service G1 said the volunteer was a 28-year-old physician who treated coronavirus patients in Rio de Janeiro.

The National Health Surveillance Agency said it was informed of the volunteer’s death Monday. The agency said AstraZeneca’s international safety committee had recommended the trial continue.

Creating a new vaccine can involve thousands of people over several years. Here's what it takes to produce a new FDA-approved vaccine. (The Washington Post)

Under the trial’s protocol, half the participants receive the experimental vaccine, and half receive an established meningitis vaccine that has been proved safe. The trial, like others, is overseen by an independent board that reviews all adverse events. Any severe event that might have been caused by the vaccine would trigger a pause in the study for an investigation. The trial is not paused due to the death.

A spokesman for AstraZeneca said he could not comment on individual cases in an ongoing trial, citing confidentiality requirements and clinical trial rules. But he said there were no concerns that would lead the study to pause.

“We can confirm that all required review processes have been followed,” spokesman Brendan McEvoy said. “All significant medical events are carefully assessed by trial investigators, an independent safety monitoring committee and the regulatory authorities. These assessments have not led to any concerns about continuation of the ongoing study.”

Oxford confirmed that the volunteer’s death was reviewed by an independent committee.

“Following careful assessment of this case in Brazil, there have been no concerns about safety of the clinical trial, and the independent review in addition to the Brazilian regulator have recommended that the trial should continue,” the university said in a statement.

The trial was suspended last month after a participant developed an unexplained illness. AstraZeneca has since resumed trials in Brazil, India, South Africa, Japan and Britain. It remains on hold in the United States.

In the global race for a vaccine, Brazil, which has been battered by the disease but has a long-standing openness to vaccines, has become one of the most crucial testing grounds. The country is hosting four vaccine trials — as many as anywhere in the world.

Brazil has watched vaccine development closely as the virus continues to lash the country. The official toll is now more than 5 million infections and over 150,000 deaths, second only to the United States. But as the tests near their conclusions, the issue of vaccinating people has become just one more issue for politicians to argue over.

São Paulo Gov. João Doria has said state health workers will begin receiving a Chinese vaccine before the end of the year. Other groups will then follow. Doria has said the vaccine will be obligatory in Brazil’s most populous state.

President Jair Bolsonaro, who has spent months touting the unvetted and potentially harmful anti-malarial drug hydroxychloroquine as a coronavirus cure, has been deeply suspicious of vaccines. He says the vaccine will not be mandatory, even though a law he signed in February said it would be.

The Chinese vaccine and Doria — a bitter political rival — have particularly irked the mercurial president.

“THE JOÃO DORIA CHINESE VACCINE,” Bolsonaro tweeted on Wednesday. “The Brazilian people WILL NOT BE ANYONE’S GUINNEA PIG.”

“My decision is not to purchase such a vaccine,” he added.

Fábio Jennings, a 47-year-old rheumatologist who has received the Oxford vaccine, said the political division gripping the country over the vaccines is nonsense. He said Wednesday he had grown to trust the Oxford vaccine more than ever.

“I’m super-calm,” he said. “Tonight, I’m going to sleep super-well.”