Dikhyaa Mohanty 
As per a study by ICMR involving 98 people, 18 of whom had inadvertently received Covishield as first dose and Covaxin as the second in Uttar Pradesh showed that combining these two COVID-19 vaccines elicited better immunogenicity than two doses of the same vaccine.
According to the reports, the study also found that immunisation with a combination of Covishield and Covaxin was safe and the adverse effects were also found to be similar when compared to the same dose regimen. The study titled Serendipitous COVID-19 Vaccine-Mix in Uttar Pradesh, India: Safety and Immunogenicity Assessment of a Heterologous Regime’ has been uploaded on medRxiv, a preprint server and is yet to be peer-reviewed.
These 18 individuals who had received one dose of Covishield and a second dose of Covaxin, 40 recipients of two doses of Covishield and 40 recipients of two doses of Covaxin, were recruited in the study. Immunogenicity profile against Alpha, Beta and Delta variants in the heterologous group was superior and IgG antibody and neutralising antibody response of the participants was also significantly higher compared to that in the homologous groups. 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.
