Outbreak of aseptic meningitis associated with mass vaccination with a Urabe-containing measles-mumps-rubella vaccine - Implications for immunizationprograms

A mass immunization campaign with a Urabe-containing measles-mumps-rubella vaccine was carried out in 1997 in the city of Salvador, northeastern Brazi l, with a target population of children aged 1-11 years. There was an outbr eak of aseptic meningitis following the mass campaign. Cases of aseptic men ingitis were ascertained through data collected from the records of childre n admitted to the local referral hospital for infectious diseases between M arch and October of 1997, using previously defined eligibility criteria. Va ccination histories were obtained through home visits or telephone calls. E ighty-seven cases fulfilled the study criteria. Of those. 58 cases were dia gnosed after the vaccination campaign. An elevated risk of aseptic meningit is was observed 3 weeks after Brazil's national vaccination day compared wi th the risk in the prevaccination period (relative risk = 14.3; 95% confide nce interval: 7.9, 25.7). This result was confirmed by a case series analys is (relative risk = 30.4; 95% confidence interval: 11.5, 80.8). The estimat ed risk of aseptic meningitis was 1 in 14,000 doses. This study confirms a link between measles-mumps-rubella vaccination and aseptic meningitis. The authors discuss the implications of this for the organization and planning of mass immunization campaigns.