Dosing Error By Researchers In The AstraZeneca-Oxford University Vaccine Trial Boosted Its Success Rate To 90%

  • AstraZeneca scientist Mene Pangalos says ‘serendipity,’ led to a break through 
  • ‘Mistake’ helped scientists discover half-dose was more effective than a full one 
  • More analysis needed to explain why an initial lower dose was more effective

A dosing error by researchers on the AstraZeneca-Oxford University Covid vaccine trial led to a huge boost in the jab’s success rate, the pharmaceutical company’s vice president has revealed.

Dr Mene Pangalos, head of AstraZeneca’s biopharmaceutical research, said the discovery that giving a half-dose at the start worked better was a lucky accident. He said: ‘The reason we had the half dose is serendipity.’ 

Volunteers were expected to receive two full doses of the vaccine. What happened with these participants would then be compared with the other half of the study group, who received a placebo.

Dr Pangalos said researchers were confused when they noticed volunteers in the vaccine group were reporting much milder side effects, such as fatigue, headaches and arm aches, than they originally predicted.  

He said: ‘So we went back and checked … and we found out that they had underpredicted the dose of the vaccine by half.’

Study results published yesterday showed that Oxford’s vaccine appeared to be up to 90 per cent effective in people who received the vaccine as a half-dose followed up by a full dose weeks later, compared to a lower 62 per cent when they were given two full doses.

Scientists explained this could be because the first smaller dose effectively prepared the immune system by showing it a small sample of the coronavirus, and then the full dose later on triggered a full-blown immune response.

Dr Pangalos said that despite the error the team decided to press ahead with the half-dose group, and to administer the second, full dose booster shot at the scheduled time.

The results showed the vaccine was 90 per cent effective among this group, while a larger group who had received two full doses produced an efficacy read-out of 62 per cent, leading to an average efficacy of 70 per cent across both dosing patterns, Dr Pangalos said.

‘That, in essence, is how we stumbled upon doing half dose-full dose (group),’ he told Reuters. ‘Yes, it was a mistake.’

It is now likely that doctors will be advised to use the 1.5 dose regimen of the vaccine rather than the full two doses because it appears to be more effective.

This will also mean that the jab, expected to cost around £2 per dose, will stretch further.

The 100million doses pre-ordered by the UK, for example, would have covered 50million people using a full two-dose system, but could now stretch to the entire population of 66million.

Although the clinical trial’s early results were published yesterday, the study is not completed.

Oxford researchers said they intend to publish the full results of the trial in a medical journal in the coming weeks and will then submit an application to the drugs regulator, the MHRA, for a licence to use the vaccine on members of the public.

This process could then take days or weeks for the MHRA to decide whether the jab is good enough to use before it can start to be given out – this is currently expected to be completed in December. 

The vaccine uses a harmless adenovirus to deliver genetic material that tricks the human body into producing proteins known as antigens that are normally found on the coronavirus’s surface, helping the immune system develop an arsenal against infection.

Dr Pangalos said more analysis was needed to explain why an initial lower dose bolstered protection. 

One possible explanation was that lower antigen levels to begin with triggered an overall better immune system build-up, he added.  

Oxford University confirmed its cheap, easy to store and simple to deliver jab could be approved by regulators in as little as a fortnight and start to be administered next month. 

Britain has ordered 100million doses, with almost 20million due by Christmas.

Professor Andrew Pollard, head of the Oxford Vaccine Group and a professor who has spent two decades running clinical trials, said that while speed of the Covid-19 vaccine’s development was in some ways extraordinary, 2020 had ‘been a very long year’ since the team started work on the vaccine in January.

That culminated this past weekend, Pollard said, in having ‘an enormous mountain to climb to pull all of the information together’ to be able to issue the early phase three trial results.

He added: ‘The last few weeks have been pretty exhausting. The feeling is absolutely one of extreme fatigue and tiredness at this point.

‘If the results have not met those regulatory requirements, they would have told us just to carry on with the trial. So it was a great relief.’

By Luke May For Mailonline and Sam Blanchard Senior Health Reporter For Mailonline

Source: DailyMail

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