Fig. 2

Dose-response relationship of neutralizing antibodies (nAbs) and vaccine efficacy (VE) against ancestral strains induced by COVID-19 vaccines. A 2-dose schedule was assumed for RNA, protein subunit, and inactivated vaccines, while 1-dose schedule was assumed for non-replicating viral vectors (as suggested by the included trials). A Dose-response relationship of nAbs against ancestral strains. nAbs were standardized as the ratio to the convalescent sera. Dashed horizontal line indicates the average level of nAbs against ancestral strains in convalescent sera. B Dose-response relationship of predicted vaccine efficacy against symptomatic infections of ancestral strains. C Association between reduction in vaccine efficacy and dose fractionation. Reductions in vaccine efficacy were measured as the ratio between vaccine efficacy against symptomatic infections of ancestral strains between fractional and standard dose groups