The risk of aseptic meningitis associated with the Leningrad-Zagreb mumps vaccine strain following mass vaccination with measles-mumps-rubella vaccine, Rio Grande do Sul, Brazil, 1997
da Silveira, C.Marcos.; Kmetzsch, C.Iris.; Mohrdieck, R.; Sperb, A.Fagundes.; Prevots, D.Rebecca.
International Journal of Epidemiology 31(5): 978-982
2002
ISSN/ISBN: 0300-5771 PMID: 12435771 DOI: 10.1093/ije/31.5.978Document Number: 244311
Background: Few data are available on the risk of aseptic meningitis following vaccination with the Leningrad-Zagreb (L-Z) strain of mumps vaccine. In 1997 the mumps vaccine was introduced into the state of Rio Grande do Sul in Brazil through mass vaccination with mumps-measles-rubella (MMR), targeting children aged 1-11 years. Five municipalities used exclusively MMR vaccine containing the L-Z strain of mumps. An outbreak of aseptic meningitis was observed shortly after the mass campaign. Methods: To estimate the risk of aseptic meningitis associated with this strain, we analysed vaccination and meningitis case surveillance data from the selected municipalities. A case of vaccine-associated aseptic meningitis was defined as one with a pleocytosis of 10-1500 leukocytes/ml and occurring within 15-35 days after vaccine receipt. Results: We estimated a risk of 2.9 cases per 10 000 doses of L-Z administered, equivalent to 1 case per 3390 doses administered. The overall risk of aseptic meningitis following the campaign was increased 12.2-fold (95% CI: 6.0-24.7) compared with the same period in 1995-1996. Following the mass campaign, the incidence of mumps declined 93% during 1998-2000. Conclusions: Vaccination with the L-Z strain of mumps vaccine as part of a mass campaign was associated with a significantly increased risk of aseptic meningitis. Decisions about type of mumps vaccine and mumps vaccination strategies must consider vaccine safety issues in addition to other criteria.