Computergest├╝tzte Epidemiologie
Mathematische Modellierung
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Estimation of the measles vaccine efficacy

During the last years there has been a resurgence of measles in industrialised nations. Vaccine efficacy and duration of immunity have, therefore, been questioned. We studied a measles epidemic that occured in the municipality of Ansbach, Germany, from June 1992 to June 1993. All general practitioneers and pediatricians of this region were asked to fill out forms concerning measles cases they had seen. According to this survey, 530 children had developed measles (89 were vaccinated and 441 were unvaccinated). The data reveiled a large fraction of vaccinated children among the cases, particularly among the older ones. The data were complemented by results of school surveys which gave us some idea of the general vaccination coverage and allowed us to estimate the age-dependend vaccination rate. Using a maximum likelihood approach, we estimated the time-dependend efficacy of the measles vaccine used in the Ansbach region. According to our results, the measles vaccine hardly provided any protection for those who were vaccinated before 1978 (estimate: 0 %; 95% confidence interval: 0-47%). In the following years, the vaccine efficacy increased to 80 % and reached 96 to 97% (95% CI: 93-99%). The estimate for the time after 7/1990 yielded a lower value of only 89% which was based on few data and, therefore, had a wide confidence interval (95% CI: 74-97%). An extended model which allowed the vaccine protection to wane over time, yielded an estimate of the loss rate of 0% per year (95% CI: 0-0,3 % per year). Statistics in Medicine kindly allowed us to provide the paper on line:

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