AN OUTBREAK OF MUMPS IN A POPULATION PARTIALLY VACCINATED WITH THE RUBINI STRAIN

Since 1991, 6 years after the recommendation of universal childhood tr iple vaccination against measles, mumps and rubella (M + M + R), Switz erland has been confronted with an increasing number of mumps cases af fecting both vaccinated and unvaccinated children. The M + M + R vacci ne mainly used in the Swiss population after 1986 contains the highly attenuated Rubini strain of mumps virus. We analysed an outbreak of 10 2 suspected mumps cases by virus isolation, determination of IgM antib odies to mumps virus in 27 acute phase sera, and verification of vacci nation histories. Mumps was confirmed by virus isolation in 88 patient s, of whom 72 had previously received the Rubini vaccine strain. IgM a ntibodies to mumps virus were detected in 24/27 acute phase serum samp les. A group of 92 subjects from the same geographic area without sign s of mumps virus infection served as controls. Ige antibodies to mumps virus and vaccination status were assessed in these children. The vac cination rate in these controls was 61%, with equal seropositivity for unvaccinated and Rubini-vaccinated subjects. These data support other recent reports which indicate an insufficient protective efficacy of current mumps vaccines.