Both Covaxin and Covishield, said to mount over 70% efficacy against virulent strains have been found to become less effective over time, and the antibody response has also been clinically found to wane, more particularly with Covaxin. Covishield has also been surrounded by controversies, over the discovery of unusual, adverse side-effects such as blood clots and neurological damage in some.
Now, while ICMR-led study is one of the first ones to be conducted in India, mixing and matching of COVID vaccines have been subjected to a lot of global studies and discussions. The most popular combination which has been subjected to trials (and also doled out to beneficiaries in certain countries like Canada and UK) includes a mix of mRNA vaccine A+ inactive viral vector virus . It has been largely observed that while the side-effects can vary from individual to individual, mixing vaccine doses is a good strategy to scale up immune response, and counter the issue of waning antibodies. In some of the cases, mixing doses was also seen to mount lifetime immunity and kick memory-B and T-cells into work, less seen with individual double-dose vaccination.