Dosing ERROR at AstraZeneca-Oxford University vaccine trial led to huge boost in jab’s success rate
Dosing ERROR by researchers in the AstraZeneca-Oxford University vaccine trial boosted its success rate to 90%, firm’s vice-president reveals
- 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 vaccine trial led to a huge boost in the jab’s success rate, the firm’s vice president has revealed.
Mene Pangalos, head of AstraZeneca‘s non-oncology research and development, said: ‘The reason we had the half dose is serendipity.’
Volunteers in Britain were expected to receive two full doses of the vaccine as it was trialed in the hope of funding a cure.
Dr Pangalos says researches were perplexed when they noticed volunteers were reporting much milder side effects, such as fatigue, headaches and arm aches, than were 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.’
Dr Mene Pangalos, from AstraZeneca, revealed a ‘mistake,’ led to one volunteer group receiving half of their first dose – but scientists later discovered that dosage was more effective than a full one
He said the team nonetheless decided to press ahead with that 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%, leading to an overall efficacy of 70% across both dosing patterns, Pangalos said.
‘That, in essence, is how we stumbled upon doing half dose-full dose (group),’ he told Reuters.
‘Yes, it was a mistake.’
The vaccine uses a harmless adenovirus to deliver genetic material that tricks the human body to produce proteins known as antigens that are normally found on the coronavirus surface, helping the immune system develop an arsenal against infection.
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 of the Oxford Universty vaccine, with almost 20million due by Christmas
Britain has ordered 100million doses, with almost 20million due by Christmas.
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 Monday’s data release showing the vaccine can be up to 90% effective.
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.’
Which is the better of the Covid-19 vaccines and how soon will we get the jabs?
There are already two other vaccines – why is Oxford’s a big deal?
Such strong results from the Oxford-AstraZeneca team gives Britain – and the world – real hope of an end to the pandemic early next year.
While the Pfizer and Moderna jabs will play a vital role, the Oxford vaccine is much better suited to mass immunisation involving billions of people.
The Oxford results also suggest that the vaccination will stop someone becoming infected and passing it on.
The previous results only showed a jab would stop someone getting ill.
Why is it easier to roll out?
The Oxford vaccine can be stored and transported in a normal fridge, while the other two require deep freeze.
Such strong results from the Oxford-AstraZeneca team gives Britain – and the world – real hope of an end to the pandemic early next year
This jab is also much cheaper – £2 to £3 per dose, compared to £15 for the Pfizer version and between £19 and £28 for the Moderna vaccine.
And the Oxford jab is based on well-established technology, meaning it is easier to manufacture at large scale.
What does it mean for Britain?
It is a huge relief for the UK Government. While ministers put in orders for seven vaccines, including 40million doses of Pfizer and 5million of Moderna, they invested most heavily in the Oxford jab – with 100million doses on order.
It is also well suited for the existing infrastructure used for the annual flu jab.
So which is the better vaccine?
The data is roughly the same, with each vaccine giving roughly 90 per cent protection at the optimal dose.
Why is an initial half dose more effective?
Scientists are not entirely sure, but believe a half dose ‘primes’ the immune system and the second full dose boosts that protection.
Giving a full dose for the first jab may lead to the immune system over-reacting and killing off the vital cells on which the vaccine relies.
How soon will we get the jabs?
The first people are likely to start receiving both the Oxford and Pfizer vaccines next month.
Scientists are not entirely sure, but believe a half dose ‘primes’ the immune system and the second full dose boosts that protection
The Medicines and Healthcare products Regulatory Agency (MHRA) had already been working on rolling assessments of both so is expected to deliver its verdicts within a week.
As soon as the formal decision is made vaccination can start immediately.
Who will get it first?
Care home residents and staff are likely to be first in line, followed by NHS staff, the elderly and those with serious conditions.
The NHS is aiming to have started vaccinating everyone on the priority lists by the end of January – including all over-50s.
Are there enough doses?
Yes – AstraZeneca has pledged to deliver enough of the Oxford vaccine for 8million people to have received their first dose by the end of December, by which time Pfizer will also have provided enough for at least 5million people.
By the end of March, AstraZeneca has pledged at least 40million full doses. With each person requiring a half dose then a full dose, that will be enough for 27million.
With Pfizer promising another 30million doses during next year, and Moderna 5million, all 52million adults in the UK should have been vaccinated by April or May.
So which vaccine will I get?
The Joint Committee on Vaccination and Immunisation (JCVI) will examine which jab is better for different groups of people, but at first glance each vaccine has a very similar profile. So it is probably going to be down to logistics.
The Oxford jab is likely to be used in GP surgeries, village halls and pop-up vaccination centres, since it can be stored in fridges.
The Pfizer and Moderna jabs will be used in the mass vaccination centres planned for conference centres, drive-through facilities and football stadiums, which will have space to set up specialist freezers.
How soon until I am safe?
It takes six weeks for immunity to kick in from the first jab. There is a gap of four weeks between the two doses, then two more weeks until protection starts.
And how long will I be protected for?
That is not yet clear, but the Oxford team believes their jab should give at least a year’s protection, suggesting everyone will need to have an annual vaccine.
The Oxford jab is likely to be used in GP surgeries, village halls and pop-up vaccination centres, since it can be stored in fridges
What are the risks?
The full data has not yet been published, but it certainly looks safe. The Oxford jab has been used on volunteers since April – with no major safety concerns – and the other two have at least two months of safety data.
Altogether more than 100,000 people have been involved in the trials which have produced data. Usually a vaccine will receive a licence after trials on 2,000 to 3,000 people.
Will it mean an end to Covid?
Experts are increasingly confident that, at the very least, vaccination will spell an end to Covid restrictions sometime next year.
Scientists have previously predicted a vaccine that gives 80 per cent protection will mean no need for social distancing – a result of more than 90 per cent is well in excess of that.
It might take some years for the world’s population to be vaccinated, and Covid may spring back from time to time, but an effective vaccine means lockdowns will become obsolete.
