COMPARISON OF SARS-COV-2 ANTIBODY PRODUCTION BY 2-DOSE CORONAVAC, 2-DOSE VAXZEVRIA, 2-DOSE CORONAVAC-VAXZEVRIA HETEROLOGOUS VACCINATION AND POST-INFECTION

Abstract

The inactivated virus vaccine CoronaVac (Sinovac) and the adenovirus vector vaccine Vaxzevria (AstraZeneca) were approved for use in Thailand to prevent coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in early 2021 but due to early supply problems in some cases a heterologous combination of the CoronaVac for the first dose followed by the Vaxzevria for the second dose was given. We aimed to compare antibody levels among subjects who received the CoronaVac only (n = 80), Vaxzevria only (n = 80), heterologous CoronaVac- Vaxzevria (n = 54) and post-infection controls (n = 91) in order to determine if the heterologous regimen is a valid vaccination option. The geometric mean antibody levels for the CoronaVac only, Vaxzevria only, CoronaVac-Vaxzevria combined regimens and post-COVID-19 controls were 96 U/ml, 818 U/ml, 797 U/ml and 78.2 U/ml, respectively. The antibody responses to the Vaxzevria only and CoronaVac-Vaxzevria regimens were not significantly different from each other (p=0.49). The mean CoronaVac-Vaxzevria heterologous regimen antibody level was significantly (p<0.0001) greater the CoronaVac only regimen. The combination CoronaVac-Vaxzevria regimen is a potentially viable option in cases with vaccine supply problems. Further studies are needed to confirm this and to determine if the CoronaVac regimen does continue to induce low antibody responses.