The effect on immunity of mixing and matching different coronavirus vaccines is to be studied in a new government-funded clinical trial.

The world-first research will determine whether mixing jabs is better than, or a good alternative to, using two doses of the same Covid-19 jab.

The idea has proven controversial amid claims that the UK was already planning to mix and match jabs, but in reality health officials advise against it except on “rare occasions”.

Deputy chief medical officer Jonathan Van-Tam, who is responsible for the study, said that mixing and matching vaccines could enhance immunity and allow the UK to carry out a more “flexible” immunisation programme

The study, dubbed Com-Cov, will initially look at mixing doses of the Oxford University/AstraZeneca and Pfizer/BioNTech vaccines, as well as different intervals between doses.

But researchers said more vaccines will be added to the list as they get approved for use.

What Happens When You Mix The Pfizer And AstraZeneca Vaccines

The team will also be looking to see whether mixing doses will offer protection against coronavirus variants.

If findings show the combined effect of the jabs is safe and induces a strong immune response, the researchers said it could lay the groundwork for introducing additional booster doses, should they be needed.

Van-Tam 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 will initially test eight different combinations, and include dosing schedules that are either 12 weeks apart or 28 days apart.

Those aged 50 and over are being called on to participate in the research, with 820 patients expected to take part.

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.

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 the study would not impact on the current rollout, telling Sky News: “It will report probably after the summer and of course it will have no impact on the deployment.

“If you have currently had the Pfizer/BioNTech vaccine, you will get your Pfizer/BioNTech vaccine as your second dose, your booster dose.

“And of course if you have the Oxford/AstraZeneca vaccine, you’ll get the Oxford/AstraZeneca vaccine.

“This is more longer-term, keeping us ahead of – at least in a leadership position, I should say – in the world, in helping the whole world because no one is safe until we are all safe.

“If we understand more about how we can use vaccines together then we should be in a much stronger position in terms of vaccinating the United Kingdom, but also the rest of the world.”