Immunogenicity of heterologous prime/boost inactivated and mRNA COVID-19 vaccine

Introduction In August 2021, Thailand imported the BNT162b2 mRNA COVID-19 vaccine. The prioritised group to receive the BNT162b2 vaccine were health professionals. The BNT162b2 vaccine scheduled for healthcare workers were two-dose regimen administered three weeks apart, the third dose booster in two-dose inactivated CoronaVac vaccine recipients or as a second dose in health professionals who had received the CoronaVac or adenoviral-vectored (ChAdOx1-S) vaccine as the first dose regardless of the interval between the first and second dose. Methods This study aims to evaluate the immunogenicity of the heterologous prime boost CoronaVac followed by BNT162b2 in health professionals. Results The CoronaVac/BNT162b2 vaccine recipients elicited higher neutralizing activity against the original Wuhan and all variants of concern than in the recipients of the two-dose CoronaVac. Conclusions The heterologous CoronaVac/BNT162b2 could be used as an alternative regimen in countries experiencing the vaccine shortages and in individuals experiencing the adverse events following CoronaVac.