Mixing Covaxin and Covishield safe, gives better immune response: ICMR

The study was conducted on 18 individuals who inadvertently received Covishield as first jab and Covaxin as second in UP at a gap of six weeks

A study by Indian Council of Medical Research has found that mixing the doses of Covishield and Covaxin was not only safe but also elicited a better immune response.

The study was conducted on 18 individuals who inadvertently received Covishield as the first jab and Covaxin as the second in Uttar Pradesh at a gap of six weeks.

The study found that the immunogenicity against Alpha, Beta and Delta variants was superior and the neutralising antibody response of the participants was also significantly higher compared to those who received both doses of the same vaccine.

The preprint study titled Serendipitous COVID-19 Vaccine-Mix in Uttar Pradesh, India: Safety and Immunogenicity Assessment of a Heterologous Regime was published on Medrxiv by ICMR and is yet to be peer reviewed.

The study compared the safety and immunogenicity profile of the 18 individuals against that of those receiving either Covishield or Covaxin. “Lower and similar adverse events following immunisation in all three groups underlined the safety of the combination vaccine-regime.”

“This is the first report of heterologous immunisation with an adenovirus vector based and an inactivated whole virion vaccine in humans demonstrating safety and significantly improved immunogenicity,” the study said.

ICMR said that the limitations of the study included that the sample size of the study was small and the follow up period is only 60-70 days after immunisation with the first dose and baseline serological and immunological data of the participants was not available.

“Despite the high median age of the participants of the heterologous group (62 years) in our study, the reactogenicity profile demonstrated that mixing of the two vaccines based on different platforms is safe," the study said.

ICMR also said that the study would have an important implication for the COVID-19 vaccination program wherein heterologous immunisation - mixing doses, will pave the way for induction of improved and better protection against the variant strains of SARS-CoV-2.

“Such mixed regimens will also help to overcome the challenges of shortfall of particular vaccines and remove hesitancy around vaccines in people’s minds that could have genesis in programmatic ‘errors’ especially in settings where multiple Covid-19 vaccines are being used,” the study added.

The study also said that to conclusively prove these findings a multicentre research trial needs to be carried out.