The effect on immunity of mixing and matching different coronavirus vaccines is to be studied in a new clinical trial funded by the U.K. government.
The world-first research will determine whether mixing shots is better than, or a good alternative to, using two doses of the same COVID-19 shot.
The idea has proven controversial amid claims that the U.K. was already planning to mix and match shots, 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 U.K. to carry out a more “flexible” immunization program.
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.
In the U.K., the Oxford University-AstraZeneca, Pfizer-BioNTech and Moderna vaccines are approved for emergency use. The U.S. hasn’t yet approved the Oxford-AstraZeneca vaccine.
The U.K. team will also be looking to see whether mixing doses will offer protection against coronavirus variants.
If findings show the combined effect of the injections 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 immunizing 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 immunization 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...