Safety and Immunogenicity of Mix-Match of Vaccines -Covishield and Covaxin – a Pilot Study

This single-center prospective observational study was conducted to assess the safety and immunogenicity of combination vaccines AstraZeneca’s ChAdOx1-nCov-19 (Covishield in India) and inactivated whole virion BBV152 (Covaxin). A total of 330 unvaccinated healthy volunteers were screened for SARS-COV2 seropositivity. RT PCR tests were conducted for seronegative volunteers (n =44). They were randomly assigned to four groups and given either same or mixed vaccines at an interval of 4 weeks between the two doses. Mix and match of vaccines did not evoke any adverse events. Combination of vaccines elicited similar immune responses in 4 groups. They were further studied dividing into homologous and heterologous vaccine groups. In Conclusion, Combination vaccines are safe and immunogenic and heterologous vaccines elicit better immunogenic response.