Mixing jabs for each dose can ward off variants, data suggest

MIXING and matching vaccines may help combat emerging variants, according to early data suggesting combining AstraZeneca and Pfizer may trigger an immune response four times stronger than two doses of the same brand.

In a small trial involving 26 relatively young patients, German researchers found levels of neutralising antibodies protecting against the Kent and South African variants were 3.9 times higher in those who had a mix of shots.

Some experts believe repeated doses of the same vaccine can blunt effectiveness over time.

Danny Altmann, a professor of immunology at Imperial College London, said the results were “not remotely surprising” as, theoretically, mixing vaccines should cancel out slight drops in efficacy when faced by new variants. “Mixing vaccines is, I think, better for tackling everything,” he said.

It comes at the start of a trial of 3,000

volunteers to see if a third vaccine dose can protect against highly transmissible variants, which, if proved, could lead to the rollout of a booster programme.

Prof Altmann said that mixing shots may become more important if people needed a third dose, either to prolong immunity or to protect against emerging variants.

There are some limitations to the German study, which was published as a preprint and has not yet been peer reviewed. And while there appears to be a strong correlation between the levels of antibodies and real-world protection, the scientists said more information was needed to ascertain the impact on transmission and disease.

“The fourfold difference we see is based on what we measured in the lab, it doesn’t necessarily translate to fourfold higher protection in the real world,” said Rudiger Gross, of Ulm University Medical Center in southern Germany. “But it is great to see that it works at least as well, possibly even a little better, than two BioNTech [vaccines], where protection is already very high.”