Oxford vaccine pause ‘a sign the system is working’

The pause, first reported by Statnews, comes only days after Prime Minister Scott Morrison announced the Federal Government had agreed to terms for around 30 million doses of the AZD1222 vaccine candidate – if it passes clinical trials.
 
Oxford University and AstraZeneca have already vaccinated approximately 17,000 people in the UK, Brazil and South Africa as part of its phase three clinical, with half receiving a control vaccine. 
 
Recruitment of another 30,000 US volunteers also began last week and before the setback it was hoped results on its effectiveness would be available by the end of the year.
 
However, the ‘potentially unexplained illness’ cited by an AstraZeneca spokesperson may affect that timeline, as it is not known how long it will take to investigate the adverse event.
 
Dr Kylie Quinn, Group Head and Research Fellow at RMIT’s School of Health and Biomedical Science,  told newsGP there is ‘not a whole lot of information’ about the nature of the adverse event, but said previous clinical trials had hinted at the candidate having ‘modestly higher reactogenicity’.
 
‘They were comparing it to a pretty well established vaccine for meningococcal disease … [which] enabled them to get good information on side effects for this particular vaccine as compared to a well established vaccine that’s out there in the clinic,’ she said.
 
‘Higher reactogenicity broadly refers to side effects that are associated with the vaccine, like soreness at the vaccine site, fever, general malaise, that sort of thing. During that clinical trial, they modified the protocol to include paracetamol to try and deal with some of those symptoms.
 
‘I’m not sure if that sort of signal relates to this particular event, but it’s something that I think there was an awareness of and it was something the Data Safety and Monitoring Board [DSMB] probably had a close eye on.’
 
Rather than being a cause for major concern, Dr Quinn said this type of event is an ‘example of the system working’ because it is what phase three trials are ‘designed to pick up’.
 
While it is not known how long the trial will be halted, Australia’s Deputy Chief Medical Officer Dr Nick Coatsworth said it could resume within days.
 
Likewise, University of Sydney vaccine expert Professor Robert Booy told newsGP the adverse event represents a ‘setback’ but is ‘not unusual’ in large scale clinical trials with thousands of participants.
 
‘[The DSMB] will independently look through the data urgently to determine if the patient had had a “live vaccine” or was a placebo recipient,’ he said. ‘Then they’ll look at the likelihood … [of] whether the vaccine caused the side effect based on the timing, and any other previously known association between the vaccine and neurological events like transverse myelitis.
 
‘They’ll be doing it urgently this week and should have information by next week as to what’s going on, and it may be possible within two to three weeks to restart the trial if there’s confidence that the vaccine is unlikely to be the cause.’
 
However, Professor Booy said the trial may continue even if the vaccine is found to have caused the reaction.
 
‘If it’s a one-off, that doesn’t necessarily mean the vaccine is ruined and can’t be used,’ he said.
 
‘That’s why it has to be weighed up by an independent group of experts who know about infectious diseases, neurological complications, vaccinology, [and] immunology.
 
‘They have to weigh up the likelihood. It may be that there’s a one rare side effect that we put up with because such a high proportion of people who get COVID are going to be in big trouble.
 
‘So the comparison of benefit and detriment could be still very strongly in favour of the vaccine.’
 
Even if the vaccine is shown to not be safe, Dr Quinn said there are many other candidates
 
‘All is not lost. This is why we have multiple vaccines that are transitioning through this clinical trial pathway,’ she said.
 
‘We have other options and other quite different options available. So that’s a really good feature … even if this particular candidate ends up not working or having issues, we can switch to quite a different type of vaccine, which spreads some of the risk.’
 
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