Epidemiology and Infection

Estimation of the basic reproduction number of measles during an outbreak in a partially vaccinated population

J. MOSSONG a1a2c1 and C. P. MULLER a3a4
a1 Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, UK
a2 CRESIS, CRP-Santé, 57 route d'Arlon, L–1140 Luxembourg
a3 WHO Collaborative Centre for Measles, Laboratoire National de Santé, P.O. Box 1102, L–1011 Luxembourg, Luxembourg
a4 Medical Faculty, University of Tübingen, 72070 Tübingen, Germany


From March to July 1996 a measles outbreak occurred in northern Luxembourg with 110 reported cases centered around two primary schools (85 cases) and the surrounding community (25 cases). Eighty four suspected cases were confirmed serologically. Vaccine coverage was estimated from questionnaire-based surveys at the two primary schools to be 70 and 76%, respectively. Vaccine efficacy during the outbreak was estimated to be 94.6% [95% confidence interval (CI) 90·4–97·0]. Using the information from the school surveys, we obtained estimates of the basic reproduction number of measles of 7·7 (95% CI 4·4–11·0) and 6·2 (95% CI 3·5–8·9), respectively. Assuming a 95% vaccine efficacy, these estimates correspond to minimal vaccine coverages of 91·6% (95% CI 81·4–95·7) and 88·3% (95% CI 75·5–93·4) which would have been necessary to minimize the chances of a major outbreak occurring. We can confirm that major outbreaks in similar school settings can only be prevented if vaccination coverage exceeds 90%.

(Accepted October 16 1999)

c1 Author for correspondence: CRESIS, CRP-Santé, 57 route d'Arlon, L–1140 Luxembourg.