Mix & Match strategy: A way forward to boost immune response?

A mix and match strategy, commonly referred to as 'heterologous prime and boost' in vaccinology parlance has ushered in promising set of results from a preliminary study conducted in Spain with 663 subjects. All the subjects included in the study had received their first dose of Oxford-AZ vaccine prior to the trial. Out of that, two-third of the subjects were randomly picked up to administer the Pfizer-BioNTech vaccine (at least 8 weeks after their first dose). The report shows the subjects who received the mRNA based vaccine from Pfizer as their second dose had elevated immune response compared to people who had both jabs of Oxford-AZ vaccine (not part of this trial) and the people who didn't receive the second dose (232 subjects in this trial). However, no comparison has been reported with people who received two doses of Pfizer vaccine and the people who received the mix and match vaccines were reported to develop higher rates of normal vaccine associated illnesses like fever and fatigue than did people who received two doses of the same vaccine. Although, the results are still premature, it promises to emerge as a potential strategy to be employed in several developing and under-developed countries having fluctuating supplies of various vaccines by simplifying immunization efforts.

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