A volunteer taking part in the trial for AstraZeneca's Covid-19 vaccine, which Australians could be given doses of, has died.
A volunteer taking part in human trials for the University of Oxford's Covid-19 vaccine has died, sparking concern and confusion over the circumstances surrounding his death.
The man has been named as 28-year-old doctor João Pedro R. Feitosa from Brazil.
He was taking part in the Brazilian trials of the coronavirus vaccine candidate being developed by the university and pharmaceutical giant AstraZeneca when he died on October 15.
No official information on the cause of his death has been given, though unofficially, it has been reported he died of complications due to Covid-19.
Equally, the vaccine developers are unable to confirm whether Feitosa was on the vaccine or the placebo as part of the trial, however an unnamed person close to the trial process revealed to Bloomberg that he had been given the placebo.
Anvisa, Brazil's National Health Surveillance Agency, confirmed on Wednesday that it had been "formally notified of the case on October 19" and had since received a report on the independent review from the security and evaluation committee overseeing the study.
It seems the trials will continue to go ahead despite the death, with organisers of the study saying the independent review concluded there were no safety concerns and that testing of the vaccine could go on.
"All significant medical incidents, whether participants are in the control group or the COVID-19 vaccine group, are independently reviewed," the University of Oxford said in a statement.
"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."
AstraZeneca also confirmed the trials would be going ahead as planned, saying an assessment of the death did not reveal "any concerns about continuation of the ongoing study".
It is understood that 50 per cent of trial volunteers are given the vaccination and the other half are given a placebo.
The developers of the vaccine would not confirm which group Feitosa was in, saying they are prevented from giving details on candidates due to medical confidentiality.
However, Bloomberg reported an unnamed person close to the trial process said Feitosa had been given the placebo.
This statement appeared to be backed up by another source familiar with the situation, with the person telling Reuters that the trial would have been suspended if the candidate was part of the group that had received the vaccine.
Mystery has also surrounded the exact cause of Feitosa's death, with officials involved in the trial again saying that data on the volunteers "must be kept confidential, in accordance with principles of confidentiality, human dignity and protection of participants".
However Brazilian media outlet, Globo, reported Feitosa, who had been working on the front lines of the pandemic, died of complications from Covid-19.
He graduated from the Federal University of Rio de Janeiro (UFRJ) last year, and was reportedly in good health prior to contracting the disease.
Following Feitosa's death, UFRJ released a statement, confirming he had died "from the Covid-19 infection he contracted while working on the front lines in the fight against the pandemic".
The university also shared a tribute written by Feitosa's girlfriend and friends.
"João, I think that in this little text I could remember how good an exemplary doctor and student you were, but I think the memory that I will mention to everyone here will be different. I want to keep forever how good a boyfriend, brother and friend you were," the statement read.
"The pain in the chest, the emptiness and longing since you left are growing in every moment and what gives us strength in that moment besides the affection of so many friends that you have made in life is to remember what you were like. The Feitosa of meaningless videos, board games, sleepless nights just talking, the friend who was always there."
His cause of death has not been confirmed by the University of Oxford, AstraZeneca, or Anvisa.
The Australian Government has already made a deal with AstraZeneca to receive and produce the vaccine should the trials prove successful.
The trial was hit by a massive setback last month after one of the participants in the UK developed an unexplained illness after receiving the shot.
Around 8000 volunteers have been vaccinated as part of the trial so far in Brazil, and more than 20,000 worldwide.
Study participants must be doctors, nurses or other health sector workers who come into regular contact with the virus.