Induction of robust neutralizing antibodies against the COVID-19 Delta variant with ChAdOx1 nCoV-19 or BNT162b2 as a booster following a primary vaccination series with CoronaVac

We determined the antibody response among CoronaVac vaccinees who were boosted with either BNT162b2 or ChAdOx1 nCoV-19. Increase in anti-S-RBD antibodies and surrogate neutralizing antibodies against the Delta variant was higher in BNT162b2 recipients than in ChAdOx1 nCoV-19 recipients. High proportions of reactogenicity were seen for both booster regimens.