Mix and match booster vaccines could soon be offered in the UK after promising trials

Ministers are consideringintroducing ‘mix and match’ coronavirus vaccines for the autumn booster shots. Early trial results show that they may provide an enhanced immune response compared to using doses from the same provider.

Mixed booster vaccines could be in the cards for autumn

So far, four different coronavirus vaccines have been approved for use in the UK, with residents being offered two doses of the same vaccine brand. But, curious researchers have been exploring the possibilities of mixing these doses and their effects on the immune response.

The UK is also considering introducing boosters in the autumn to provide extra protection against existing and emerging coronavirus strains that have some resistance to current vaccines. The government revealed that mixed jabs might also be introduced for the boosters by giving residents a different type of shot than their previous two.

Early studies show mixed vaccines could provide enhanced immunity

Trials on the effectiveness of mixed doses are taking place all over the world, with the UK’s Com-Cov study - launched in February - exploring mixes of Pfizer, Moderna, AstraZeneca and Novavax vaccines. Separate trials from both Spain and Germany have also shown promising results.

Another study from Germany compared the immune response of 26 people aged 25-46 who each had one dose of the AstraZeneca vaccine followed by a second shot and a booster of the Pfizer jab. Results showed that the mixed vaccine approach provided neutralising antibodies against the Alpha variant almost four times higher than the median amount.

Neutralising antibodies against the Beta and Delta variants were also increased but not to the same level as the Alpha variant. Still, the immune response was more robust than those given two doses of the Pfizer vaccine.

Results of the study call for more research and a larger, more varied cohort of participants; still, initial results are very promising. Lawrence Young, a virologist and professor of molecular oncology at the University of Warwick, revealed to The Guardian that the results were not surprising as the use of varying vaccine technologies would have allowed for a more diverse immune response. He continued:

Nevertheless, mix and match vaccination bodes well for the future efficacy of booster shots to soup up protective immunity against virus variants. These booster jabs may be even more effective if tweaked to include the variant spike proteins – something currently being trialled by Moderna and very soon by other vaccine manufacturers.

Prof Deenan Pillay, a professor of virology at University College London, expressed that mixing vaccines could introduce flexibility and take some of the pressures away from vaccine supplies. However, he also pointed out that mixing vaccine doses could also provide increased side effects.

Preliminary findings from the Com-Cov study expressed that mixing coronavirus vaccines increased the chances of developing mild side effects. However, none of the side effects were classed as severe or harmful.