A serosurvey evaluation of the school-based measles 'catch-up' immunisation campaign in Victorian school-aged children

Objective: To determine the proportion of Victorian primary school students protected against measles infection one year after the completion of the measles 'catch-up' immunisation campaign of 1998 and to compare this with the proportion of year 9 and 10 (aged 14-16 years) students. Design & setting: Three-stage random cluster survey in Victorian primary and secondary schools. Main outcome measures: Proportion of primary and year 9 and 10 secondary school students protected against measles infection one year after the completion of the mass 'catch-up' immunisation campaign. Secondary outcomes: the proportion of both primary and year 9 and 10 secondary school students protected against both mumps and rubella. Results: Of 1,037 Victorian primary and 2,357 years 9 and 10 secondary school students invited to participate in this study, 403 (39%) and 752 (32%) respectively provided a blood specimen for serological testing for antibodies against measles, mumps and rubella. 94.8% (95% confidence interval, 91.5, 96.9) of primary school and 93.1% (90.9, 94.8) of year 9 and 10 students were protected against measles infection. Conclusion: One year after the completion of the school-based measles 'catch-up' immunisation campaign the level of protection in Victorian primary school aged students is sufficient to prevent the continuing circulation of measles virus within this age group. The proportion of year 9 and 10 secondary school students protected against measles is also probably sufficient to prevent continuing circulation of wild type virus in Victoria, even though this age group was not specifically targeted by the 'catch-up' campaign.