Fig. 3

Population-level impact in counterfactual scenarios of booster vaccination. The daily incidence of SARS-CoV-2 infections is shown by counterfactual scenario of booster vaccination in Tokyo. The orange dots represent the empirically observed data (confirmed cases divided by an ascertainment bias factor of 25%). Three scenarios were explored: (i) the vaccination coverage on the last day of the study period (May 27, 2022) was equivalent to that of the primary series (Equiv. to 2nd dose coverage), (ii) the vaccination coverage was equivalent to that of the second booster (i.e., the 4th dose), which was administered later in 2022 (Equiv. to 4th dose coverage), and (iii) the vaccination coverage among people aged 10–49 years was 10% greater than that of the observed third dose (Elevated coverage). Further details can be found in the Additional file