The regime for both the vaccines initially included a second homologous booster dose following a priming dose at an interval of four weeks
Immunization with a combination of first dose of Covishield followed by second dose of Covaxin is not only safe but also elicits better immunogenicity, the Indian Council of Medical Research (ICMR) said on Sunday citing its preprint research.
When peer reviewed and recognized, the research may pave the way for more flexibility in mixing and matching covid-19 vaccines in India.
The programme for immunization against covid-19 in India started with the two vaccines on 16 January. Covishield is the in-country version of the Oxford-AstraZeneca vaccine manufactured by Serum Institute of India, while Covaxin is an inactivated whole virus vaccine (BBV152) developed jointly by ICMR-National Institute of Virology (ICMR-NIV) and Bharat Biotech International Ltd.
The regime for both the vaccines initially included a second homologous booster dose following a priming dose at an interval of four weeks. With gradually emerging evidence, the gap between the two doses of Covishield was increased to six to eight weeks and later to 12 weeks.
A group of individuals in Uttar Pradesh received Covishield as the first dose followed by inadvertent administration of Covaxin as the second dose at an interval of six weeks.
“We compared the safety and immunogenicity profile of them against that of individuals receiving either Covishield or Covaxin (40 in each group). Lower and similar adverse events following immunization in all three groups underlined the safety of the combination vaccine regime," said the authors.
“The immunogenicity profile against Alpha, Beta, and Delta variants in the heterologous group was superior. The IgG antibody and neutralizing antibody response of the participants was also significantly higher compared to that in the homologous groups," ICMR said in the study.
The apex biomedical research organization maintained that the findings suggest that immunization 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.
“Overall, this study demonstrates that immunization 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.
These findings have an important implication for the covid-19 vaccination programme in which heterologous immunization will pave the way for the induction of improved and better protection against the variant strains of SARS-CoV-2, ICMR said.
Such mixed regimens will also help overcome the challenges of shortfall of particular vaccines and remove hesitancy around vaccines in people’s mind that could have genesis in programmatic ‘errors’, especially in settings where multiple covid-19 vaccines are being used, it added.
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