PUNE/NEW DELHI: A combination of Covishield and Covaxin could not only be safe but elicits better immune protection and the adverse effects were no different as a same vaccine regimen, ICMR’s analysis of a “serendipitous” Covid-19 vaccine-mix in Uttar Pradesh shows.
The study examined 18 individuals in UP who inadvertently received Covishield as the first jab and Covaxin as the second. Researchers compared the safety and immunogenicity profile of this group with two groups of individuals who received either Covishield or Covaxin.
“The findings suggest that immunisation with a combination of an adenovirus vector platform-based vaccine followed by an inactivated whole virus vaccine was not only safe but also elicited better immunogenicity,” the pre-print of the Indian Council of Medical Research study published in MedRxiv says.
The blood samples of the 18 individuals who were mistakenly given Covishield and then Covaxin jabs in April-May were analysed at different stages for 60 to 70 days after vaccination.
“The mix-and-match of Covishield and Covaxin as first and second dose provoked a superior immune response than two doses of either Covishield or Covaxin,” said senior ICMR scientist Rajni Kant, the study’s chief investigator. This is the first report of mixed immunisation that has demonstrated safety and significantly improved immune response.
The findings are important as experts have asked if Covishield and Covaxin doses can be mixed to get around supply shortages. Currently, deliberate mixing of the two vaccines is not advised. But to conclusively prove these findings, the ICMR researchers said a multicentre randomised controlled trial (RCT) would be needed as the current sample size was small.
Findings show immunogenicity profile in people who received both the vaccines was superior against Alpha, Beta and Delta variants, IgG antibody and neutralising antibody response was significantly higher compared as in the case of homologous groups. “To the best of our knowledge, this is the first study which reports the effects of heterologous prime-boost vaccination with an adenovirus vectored vaccine followed by an inactivated whole virus vaccine,” the researchers said.