Number 10 has launched the world’s first trial into whether mixing and matching coronavirus vaccines is safe and can enhance protection against the disease.
The study of more than 800 patients will look at the effect of giving someone an initial dose of the Oxford University jab, followed by the Pfizer one, and vice versa.
Scientists will trial other vaccine combinations as more are approved and rolled out across the UK over the course of the year-long research.
Experts believe the ‘mix and match’ approach could stimulate different parts of the immune system and give better, longer lasting immunity.
The tactic could also help Britain deal with supply shortages which has held back the UK’s otherwise successful vaccination rollout.
The study, run by the National Immunisation Schedule Evaluation Consortium (NISEC), will investigate whether mixing vaccines can protect people from new variants of the virus.
UK regulators have so far only approved giving patients two doses of the same vaccine and the new study will not impact anyone currently being invited for a jab.
Currently the Oxford University/AstraZeneca and Pfizer/BioNTech Covid vaccines are the only two being rolled out in the UK.
Ten million Brits have had at least one dose of either. A third, made by Moderna, has been approved but supplies won’t arrive until spring.
Two other vaccines, including ones made by Johnson and Johnson and Novavax, are on the cusp of being approved and several more promising candidates are in late stage trials.
Number 10 has launched the world’s first trial into whether mix-matching coronavirus vaccines is safe and provides high protection against the disease
Deputy Chief Medical Officer and Senior Responsible Officer for the study, Professor Jonathan Van-Tam said: ‘This study will give us greater insight into how we can use vaccines to stay on top of this nasty disease’
The new study, named Com-Cov, will initially look at mixing doses of the Oxford and Pfizer vaccines, as well as different intervals between doses.
The study will initially test eight different combinations, and include dosing schedules that are either 12 weeks apart or 28 days apart.
Blood samples will be taken over time to measure antibody levels – proteins which indicate how much protection someone has – in the participants.
If findings show the combined effect of the jabs is safe and induces a strong immune response, the researchers say it would make vaccine implementation more flexible and lay the groundwork for introducing additional booster doses, should they be needed.
Those aged 50 and over – who are most at risk of falling very ill with Covid – are being called on to participate in the research, with 820 patients expected to take part in total.
They will be recruited over the course of February through the NHS Covid-19 Vaccine Research Registry, with initial results expected to become available during the summer – ‘in time to inform policy use of booster vaccines amongst younger cohorts’.
The team will also be looking to see whether mixing doses will offer protection against coronavirus variants, including the alarming strains that emerged in South Africa, thought to be spreading in the community in Britain, and Brazil.
Both appear somewhat resistant to the current crop of two-dose vaccines, although not enough to make them useless.
The researchers will do this by taking blood samples from people who have been given a mix-matched dosing regimen and exposing it to the new variants in a lab.
It is not yet known what the effects are of mixing vaccines which use completely different technology.
Pfizer and Moderna’s, for example, use brand-new mRNA technology, which utilises copy of a natural chemical called messenger RNA to produce an immune response.
Oxford’s, on the other hand, uses a traditional adenovirus vector, a weakened form of the common cold which carries instructions to cells teaching them to fight Covid.
Deputy Chief Medical Officer Professor Jonathan Van-Tam, who is the senior responsible officer for the study, said: ‘Given the inevitable challenges of immunising large numbers of the population against Covid-19 and potential global supply constraints, there are definite advantages to having data that could support a more flexible immunisation programme, if needed and if approved by the medicines regulator.
‘It is also even possible that by combining vaccines, the immune response could be enhanced giving even higher antibody levels that last longer; unless this is evaluated in a clinical trial we just won’t know.
‘This study will give us greater insight into how we can use vaccines to stay on top of this nasty disease.’
The study is being run by the National Immunisation Schedule Evaluation Consortium (NISEC) across eight different sites across England – which includes London, Oxford, Southampton, Birmingham, Bristol, Nottingham and Liverpool.
The research is the first to determine the effects of using different vaccines together to protect against Covid-19.
This approach, where vaccines work better if a different jab is used for boosting, is known as heterologous boosting and is used in certain types of vaccines such as hepatitis B and tuberculosis.
Vaccines minister Nadhim Zahawi said: ‘This is a hugely important clinical trial that will provide us with more vital evidence on the safety of these vaccines when used in different ways.
‘Nothing will be approved for use more widely than the study, or as part of our vaccine deployment programme, until researchers and the regulator are absolutely confident the approach is safe and effective.
‘This is another great step forwards for British science, expertise and innovation, backed by Government funding – and I look forward to seeing what it produces.’
Dr Andrew Garrett of ICON Clinical Research added: ‘This is a welcome announcement and the trial represents a positive step forward, both in the UK and internationally.
‘It initiates the next stage of vaccine development, which is to establish optimal dosing for approved vaccines and their combinations.’
It comes after the UK passed the landmark of 10million vaccine doses yesterday, amid hopes that all adults could have received Covid jabs by the end of August. Around 353,000 jabs were administered on Monday.