Figure 2.

Comparative effectiveness of allocation strategies of vaccines and antivirals in Japan assuming all vaccinees received the BNT162b2 vaccines. As of 1 August 2021, 39.7% of the population had taken at least first dose of vaccine and all of them received the BNT162b2 vaccines. We assumed that the effective reproductive number before the vaccination program (R_e) was 6 and that the effects of vaccination (characterized by σ_m, σ_t, and σ_s) were realized instantaneously after the target vaccine uptake was achieved. For Strategy 4, the additional dose would be given to vaccinees with the original PRNT50 titre lower than 74.1, which corresponded to the estimated thresholds of 70% protection against the original virus. The epidemics were seeded with one introduction event immediately after the target vaccine uptake was achieved. We assumed PRNT50 titres reduced by 4, 7 or 10 folds due to VOCs and one dose of booster vaccine increased the PRNT50 titres by 3 or 9 folds (i.e., b = 3 or 9). We assumed the target vaccination coverage (c) was 70%, 80% or 90%. (A) The total number of hospitalisations per thousand population. (B) The maximum daily number of hospitalisations per thousand population. (C) The number of hospitalisations averted per thousand vaccine doses, compared with the existing vaccine uptake as of 1 August 2021 (i.e., about 39.7% coverage).