Resumo

LEE, Min-Shi  e  NOKES, D. James. Predicting and comparing long-term measles antibody profiles of different immunization policies. Bull World Health Organ [online]. 2001, vol.79, n.7, pp. 615-624. ISSN 0042-9686.  http://dx.doi.org/10.1590/S0042-96862001000700006.

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.

Palavras-chave : Measles [immunology]; IgG [immunology]; Measles vaccine [administration and dosage]; Measles vaccine [immunology]; Forecasting [methods]; Child; Child, Preschool; Immunization programs; Health policy; Seroepidemiologic studies; Models, Theoretical; Taiwan, China.