Predicting and comparing long-term measles antibody profiles of different immunization policies

objective: measles outbreaks are infrequent and localized in areas with high coverage of measles vaccine. the need is to assess long-term effectiveness of coverage. since 1991, no measles epidemic affecting the whole island has occurred in taiwan, china. epidemiological models are developed to predict the long-term measles antibody profiles and compare the merits of different immunization policies on the island. methods: the current measles immunization policy in taiwan, china, is 1 dose of measles vaccine at 9 months of age and 1 dose of measles, mumps and rubella (mmr) vaccine at 15 months of age, plus a ？mop-up？ of mmr-unvaccinated schoolchildren at 6 years of age. refinements involve a change to a two-dose strategy. five scenarios based on different vaccination strategies are compared. the models are analysed using microsoft excel. findings: first, making the assumption that measles vaccine-induced immunity will not wane, the predicted measles igg seroprevalences in preschool children range from 81% (lower bound) to 94% (upper bound) and in schoolchildren reach 97-98% in all strategy scenarios. results are dependent on the association of vaccine coverage between the first and second dose of vaccine. second, if it is assumed that vaccine-induced antibody titres decay, the long-term measles seroprevalence will depend on the initial titres post vaccination, decay rates of antibody titres and cut-off of seropositivity. conclusion: if mmr coverage at 12 months of age can reach >90%, it would be worth changing the current policy to 2 doses at 12 months and 6 years of age to induce higher antibody titres. these epidemiological models could be applied wherever a similar stage of measles elimination has been reached.