If V and N denote numbers of vaccinated individuals and the total population size respectively, then vaccination coverage can be expressed as a proportion P ¼ V/N. The number of vaccinated dogs declines following a campaign as individuals die and as vaccineinduced immunity wanes (V t ¼ V 0 e -(dþm)t , where d is the death rate and 1/m is the duration of vaccine-induced immunity), whereas the total population grows at the rate of population increase (N t ¼ N 0 e rt ). To prevent sustained endemic transmission, vaccination coverage must be maintained above P crit (such that R is held below 1). From our estimates of demographic parameters and R 0 , we calculated the proportion of the population that needs to be vaccinated, P target , to prevent vaccination coverage falling below P crit during the interval, T, between campaigns: P target ¼ e (mþdþr)T P crit . This formulation for estimating the coverage needed to interrupt endemic transmission given turnover in the domestic dog population assumes that immunity from vaccination lasts an average of 1/m time units and declines exponentially. In reality, vaccine-induced immunity is likely to be closer to a fixed duration, and thus fewer dogs would be expected to lose immunity during the 1-y interval between campaigns than under the exponential model. This indicates that our estimate of P target may be slightly overestimated, although this is an important area for further investigation.