The Brazilian health authority Anvisa on Wednesday said that a volunteer involved in the clinical trial of the COVID-19 vaccine candidate being tested by AstraZeneca and Oxford University had died. However, the trial is set to continue. Oxford confirmed the same in a statement saying that post careful assessment, “there have been no concerns about safety of the clinical trial.” AstraZeneca reportedly did not comment on the issue owing to confidentiality and clinical trial rules. A Federal University in Sao Paulo also said that an independent review committee’s recommendation was also for the trial to continue.

However, other reports have said that the volunteer who died had not actually taken the vaccine shot, a source “familiar with the matter” has said. Per a report in the Brazilian newspaper O Globo, sources said that the volunteer was administered a placebo and not the actual vaccine. A source also told Reuters that had the volunteer been given the COVID-19 vaccine and then died, the trial would have been suspended. The volunteer was given a meningitis shot, said the source.

While it is confirmed that the volunteer who died is Brazilian, other details are not known. While a total of 10,000 volunteers are to receive the first dose of the vaccine in six Brazilian cities, 8,000 have gotten it, and many have gotten the second dose too.

After this news, AstraZeneca shares fell by 1.8%.

This is not the first time the Oxford-AstraZeneca vaccine has run into trouble. Earlier, the trial was paused after a volunteer in the UK fell ill after being administered a shot. However, the trial resumed in the UK, Brazil, South Africa and India recently, while it continues to be on hold in the US. In India, the Serum Institute of India has permission to run this vaccine’s phase 2 and phase 3 clinical trials.