Fig 2. Vaccination coverage required for herd immunity.

A: Vaccine coverage V_threshold required to achieve herd immunity threshold as a function of the reproduction number R₀ for the USA demography and contact structure where $R_{\text{critical}}^{20+}$ and $R_{\text{critical}}^{10+}$ correspond to beproduction numbers at which herd immunity cannot be achieved without vaccination of age groups 0 − 19 and 0 − 9, respectively. B: Vaccine allocations at which herd immunity is achieved at minimal vaccine coverage and when all the population is eligible for vaccination. C: Same as B, but when ages ten and older are eligible for vaccination.