Effectiveness of measles vaccination after household exposure during a measles outbreak - A household contact study in Coburg, Bavaria

Background: A measles outbreak was recently observed in Coburg, Bavaria, in a population with vaccination rates of 76.5% in 5- to 6-year-old children in the years preceding the outbreak. Only a small proportion of children had received 2 vaccinations against measles. Vaccine effectiveness is estimated in a household contact study and also by a screening method. Methods: A household contact study was conducted in families with at least I measles case by standardized computer-assisted telephone interviews to assess secondary attack rate and to estimate vaccine effectiveness. Vaccine effectiveness was also estimated with Farrington's screening method with information from school entry examinations and from questionnaires of confirmed measles cases in the Coburg outbreak. Results: Thirty-eight children were primary cases. Of their contacts, 20 children were included in the study as secondary cases (I vaccinated), and 23 children were contacts who did not develop measles (12 vaccinated once and 4 vaccinated twice), resulting in a vaccine effectiveness of 90% (95% confidence interval, 35-97%) for one vaccine dose. The proportion of the population vaccinated reached 81.5% during the outbreak and the proportion of the cases vaccinated was 10.9%, resulting in a vaccine effectiveness estimated using the screening method of 97.2% (95% confidence interval, 95.7-98.3%). Conclusions: With the use of 2 approaches to estimate the effectiveness of measles vaccination, a consistently high vaccine effectiveness of 90% or above was shown during a measles outbreak in Western Europe.