A study done by ICMR on the cocktail vaccine, mixing Covaxin and Covishield, has received the approval of Drugs Controller General Of India (DCGI).  The cocktail is found to be safe, effective and offering better immunity, according to the study. 

Covaxin is an inactivated whole virus vaccine, while Covishield is an adenovirus vector platform-based vaccine. Interestingly, a mistake resulted in the study. 18 villagers in Uttar Pradesh had earlier got a Covaxin shot, 6 weeks after getting a dose of Covishield.

Studies on those 18 recipients were done and the results were compared to that of those 40 recipients who received Covaxin and the other 40 who got double shots of Covishield. “Overall, this study demonstrates that immunisation with a heterologous combination of an adenovirus vector platform-based vaccine followed by an inactivated whole virus vaccine is safe and elicits better immunogenicity than two doses of homologous vaccination, using the same vaccines,” the study said

The study, however, is not peer-reviewed.

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“While ICMR using a mistake to get some preliminary data on heterologous vaccination is commendable, there is no great novelty in the approach. These results are really preliminary because it examines only 18 individuals with mixed vaccination,” immunologist Dr Vineeta Bal told Indian Express. “There is no easy immunological explanation in the present case… The data shows that heterologous vaccination triggers better antibody response as compared to two shots of Covaxin. However, there is no such enhancement seen with two shots of Covishield,” she added.

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According to the World Health Organization, there is only limited data on the efficacy of a “mix and match” regimen at present. “WHO is of the view that the mix-and-match regimens are likely to work. However, we really need to analyse the evidence in each of these vaccine combinations before any other recommendations can be made,” the WHO said in an email.

Leading vaccine scientist Dr Gagandeep Kang said, “regulators know only what companies have done — and mix-and-match studies do not usually come under their purview as applications from companies, because companies want to sell two doses of their product, not one in combination with another company’s product”

“When academics do studies, they want to characterise immune response and understand whether it is strong and long-lasting. All this is a process of learning and we have a long way to go and not just take limited information and draw large inferences,” he added.