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Questions raised about the Oxford AstraZeneca coronavirus vaccine

1 December 2020

5:31 PM

1 December 2020

5:31 PM

As discussed in this publication by Professor Jennifer Rogers last week, there have been discrepancies in the data reported by AstraZeneca in its trial of the coronavirus vaccine. Professor Rogers noted in particular: 

We are told that one dosing regimen (with a sample size of 2,741 participants) showed efficacy of 90 per cent when the ChAdOx1 nCOV19 vaccine was given as a half dose, followed by a full dose at least one month apart, and another dosing regimen (with a sample size of 8,895) showed 62 per cent efficacy when given as two full doses at least one month apart. The estimated efficacy for the half dose gave a higher result than that estimated for the full dose. This seems counterintuitive and unexpected. But the sample size for the half dose was smaller than for the full dose and so the point estimate of 90 per cent efficacy for the half dose will be subject to more uncertainty than for the full dose. 

This has led to comparisons being drawn with the Pfizer and Moderna vaccine candidates. However, Professor Rogers asserts making such comparisons is unhelpful:

Direct comparisons of results from different trials should generally be done with caution due to differences in study population, endpoints, and regions. If one wishes to carry out a comparison of the vaccine efficacy of multiple candidates, this should be done in a head-to-head clinical trial. Otherwise, you are not comparing apples with apples. 

Her conclusion, though, is a positive one:  

This study also carried out monitoring for asymptomatic infection and we are yet to see these results although we are told that early indications suggest the vaccine ‘could reduce virus transmission from an observed reduction in asymptomatic infections’. Crucially, this vaccine has a huge advantage over others in the way that it is stored. The Oxford-AstraZeneca vaccine will be easily administered in existing healthcare systems, stored at fridge temperature and distributed using existing logistics. Vaccine efficacy is just one part of the puzzle.

The discrepancies noted in the Oxford vaccine data, however, deserve further scrutiny. An Australian immunologist, Dr Geoff Porges, has undertaken this scrutiny and, in his view, there are legitimate concerns. In an interview with the ABC last week, he asserted that AstraZeneca had ‘embellished the data’. Such concerns are raised specifically in relation to the ‘full dose’ versus ‘half dose’ mystery outlined above. 

As the ABC report stated, the company later acknowledged that the half dose was a “manufacturing issue” and given to the trial participants by mistake. It also revealed only 2,741 people had been given the half dose while 8,895 people received the two full doses.  

Facing increasing pressure to clarify the data, AstraZeneca chief executive Pascal Soriot said on Friday it would now likely conduct a new global clinical trial to assess the vaccine’s efficacy. 


Other immunologists have weighed in on the matter: “[AstraZeneca] hasn’t handled it the best,” RMIT immunology and vaccine expert Kylie Quinn said. 

The error in the dosing is disappointing, disappointing to hear that that would happen at this particular point in time. 

“But this whole situation highlights the importance of clear communication of exactly what’s being done. 

Dr Porges added: “Confidence comes from transparency of communication and clarity of communication. 

You need to be completely honest about what you’re sharing and really clear about the information. 

And I think AstraZeneca, at the very least, violated those two tenets.” 

While Professor Rogers, Dr Porges and Dr Quinn remained confident generally in the efficacy and safety of a coronavirus vaccine, the issues in relation to the data reported by AstraZeneca should raise legitimate concerns. 

Just like Pfizer and Moderna, AstraZeneca has had its fair share of litigation over the years across the globe. It has had to pay fines and settlements amounting to the billions of (US) dollars in relation to: 

As I wrote recently, this is the kind of company governments around the world (including Australia’s) want to trust with producing a safe and effective vaccine. More to the point, this is the vaccine Scott Morrison, Greg Hunt and Alan Joyce practically want to extort us into taking. 

For those who place a high value on ethics, it seems, even with the coronavirus vaccine trial, AstraZeneca has some serious questions to answer.

Such questions become even more critical given the indemnities granted by the government to AstraZeneca (and potentially other pharmaceutical companies) covering liabilities that could result from the vaccine. 

Dr Rocco Loiacono is Senior Lecturer at the Curtin University Law School.

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