Safety evaluation of MMR vaccine during a primary school campaign in Saudi Arabia.

Monitoring of adverse events following the administration of MMR vaccine containing the Urabe mumps virus vaccine strain, to over 2 million schoolchildren (aged 6-13 years) revealed that the incidence of vaccine-associated aseptic meningitis was one case per 295 000 doses given. About 92 per cent of these children had had their primary immunization against MMR at 12 months of age and, therefore, were probably not immunologically naive. It appears from our data that the use of the Urabe-based mumps vaccine in the booster-dose format induces much less adverse effects than usually observed following the primary immunization with it. Further studies are needed to prove this conclusively.