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expert reaction to media reports suggesting a person in Brazil who was taking part in the Brazil arm of the Oxford/AstraZeneca vaccine trial has died

It has been reported that a person in Brazil who was taking part in the Brazil arm of the Oxford/AstraZeneca COVID-19 vaccine trial has died.


Prof Eleanor Riley, Professor of Immunology and Infectious Disease, University of Edinburgh, said:

“Details on this are very sketchy at present but Brazil currently has one of the highest per capita death rates in the world for Covid-19.  So, whilst to be greatly regretted, a death from Covid-19 among clinical trial participants (if that is what has happened, as some media reports are suggesting) is not unexpected.

“The individual concerned may or may not have received the Covid-19 vaccine – half of the participants in the trial will have received a placebo vaccine – and even if they had received the active vaccine it would be remarkable if it were 100% effective.

“The key questions to be answered are whether or not the individual had received the active vaccine and, if so, whether their death was a typical Covid-19 death or whether there were any indications that the vaccination contributed to the death.  In the absence of such information it is unwise to speculate.

“Every reputable clinical trial, such as this trial being undertaken by the Oxford/Astra Zeneca partnership, is overseen by an independent data and safety monitoring board.  This board will have reviewed the case in detail before be reviewing the data in detail before liaising with the Brazilian and international regulators before determining that the trial can continue.”


Dr Andrew Freedman, Reader in Infectious Diseases and Honorary Consultant Physician, Cardiff University School of Medicine, said:

“Any serious adverse event, including death of a participant in a clinical trial is, of course, thoroughly investigated.  This would include ‘unblinding’ to ascertain whether the subject was in the active or control arm.  If they had received the investigational agent, in this case the trial vaccine, the next step would be to determine whether the event was likely to be have been caused by the vaccine itself or by something unrelated.  In many cases this will be fairly easy, but in others it may take some time to investigate and the trial would be paused until the regulatory authorities determine that it is safe to resume.

“Fortunately, deaths resulting from the administration of a trial drug or vaccine are very rare and would normally lead to the immediate discontinuation of the trial.”


Prof Ian Jones, Professor of Virology, University of Reading, said:

“Without details it’s impossible to know what has happened in this case but as the trial is continuing, I think we can assume the circumstances of the death were such that it was clearly not vaccine related.  What we have to remember is that in any large trial the normal processes of morbidity and mortality are still operating and that sometimes an event will occur in a trial participant which would have occurred anyway, trial or not.  The case will have been carefully examined and, as vaccine relatedness has presumably been ruled out, the trial should continue to bring the vaccine to a decision point as soon as possible.”


Prof Trudie Lang , Director, The Global Health Network, Nuffield Department of Medicine, University of Oxford, said:

“In vaccine trials every participant has every medical event recorded throughout the time they are taking part in the trial.  This happens in exactly the same way for those receiving the experimental vaccine and for those receiving the comparator or placebo vaccine.  As these trials are ‘blinded’ neither the clinicians looking after these participants or the participants themselves know which vaccine they have had.  It is important to keep in mind that vaccine trials follow these participants for many months in order to see whether or not they develop the disease that the vaccine is aiming to prevent.  Therefore, during this time medical events are likely to occur and these are all recorded and carefully reviewed to assess whether or not they are considered to be even possibly related to the vaccine.  These medical events are defined as ‘adverse events’ and categorised as serious, or non-serious.  The sad event of someone dying on a vaccine trial immediately triggers the actions defined in the trial protocol that are carefully set out for all serious events.  Here the cause of death would be reviewed by an independent safety monitoring committee and the regulatory authorities.  They may decide to ‘unblind’ a case and see which vaccine the participant received, if they decide the nature of the event requires them to assess whether this specific event was related to the vaccine or not.  It may not always be necessary to unblind the case, as it might be an event clearly unrelated, such as a road traffic accident.  We do not know the details in this situation but the robust and independent oversight processes within all such vaccine trials would have reviewed this sad event and concluded that there is no requirement to stop the trials, and therefore there is no new evidence to suggest that this vaccine is not safe.”




Statement from the University of Oxford:

“All significant medical incidents, whether participants are in the control group or the Covid-19 vaccine group, are independently reviewed.  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.”



All our previous output on this subject can be seen at this weblink:


Declared interests

Prof Eleanor Riley: “No COI.”

Dr Andrew Freedman: “I am lead PI for COVID Vaccine trials in Wales but have had no involvement in the Oxford trial.”

Prof Ian Jones: “No conflicts.”

Prof Trudie Lang: “No conflicts of interest.”

None others received.

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