[Mumps epidemiology in Switzerland: results from the Sentinella surveillance system 1986-1993. Sentinella Work Group]

Since 1990, there have been reports of an increasing number of mumps cases in Switzerland, in particular among vaccinated children, and of local outbreaks of mumps. Using data from the Sentinella reporting system, a network of voluntary participating doctors (general practitioners, internists and paediatricians, yearly average: n = 141), trends and factors influencing mumps incidence in the general population were assessed during the last seven years. Following an initial decline in mumps reports, since 1990, there has been a continuous and marked increase in reports from a minimum of 0.7 cases per physician and year in 1989/90 to a near five-fold increase of 3.3 cases in the last reporting period from June-December 1993 (calculated for one year). Half of this increase, which is reflected in a doubling of the number of cases reported in 1986/87, is explained by an increase in cases among vaccinated children. The trend in mumps cases contrasts with that of measles and rubella, where there has been a clear decline in these reports since 1986 (approximately 70-80%). Complications were reported in 75 (4.0%) of the total number of mumps patients (n = 1894); in 2/5 of the cases this was a meningitis, in 1/3 an orchitis. Based on available data on vaccination coverage, the estimated efficacy of the mumps vaccines against parotitis is between 47-77%; this is clearly lower than the corresponding figure for measles (91-97%) and rubella (89-97%) vaccines. The relatively low efficacy against parotitis is mainly due to a protective level of 13-73% of the vaccines containing the Rubini strain. The estimated efficacy of the Rubini vaccines against complications is 50-81%; it is nearly 60-90% if a possible reporting bias is taken into consideration.

1. The Rubini strain vaccines, which are the most commonly used in Switzerland, seem to have played an important role in the clear increase in mumps cases since 1990. 2. The situation seems more favourable concerning the efficacy against complications of the vaccines used. 3. Our data support the high efficacy of all measles and rubella vaccines. 4. The surveillance of MMR by the Sentinella reporting system provides a useful and effective manner to evaluate the MMR vaccination programme.