According to sources, the ICMR-led study was ordered after some people in UP accidentally received mixed doses of Covaxin and Covishield, and said there were no side effects. While the study, which is yet to be reviewed, established that beneficiaries registered a higher than normal antibody response, the combination of Covishield and Covaxin was also reported to be safe and effective.
Both Covaxin and Covishield noted that more than 70% efficacy against virulent strains has become less effective over time, and the antibody response has also decreased clinically, particularly with Covaxin. Covishield has also been embroiled in controversy over the discovery of unusual, adverse side effects in some, such as blood clots and neurological damage.
Now, while the ICMR-led study is one of the first to be conducted in India, there have been a lot of global studies and discussions on mixing and matching COVID vaccines. The most popular combination that has been subjected to trial (and also distributed to beneficiaries in some countries such as Canada and the UK) involves a mixture of mRNA vaccine A+ inactivated viral vector virus. It has been largely observed that while side effects may vary from person to person, mixing vaccine doses is a good strategy to enhance the immune response and counteract the issue of antibody depletion. In some cases, mixed doses were also seen to enhance lifelong immunity and activate memory-B and T-cells, which were less observed with individual double-dose vaccination.
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