Aseptic Meningitis Outbreak Linked to Widespread MMR Vaccination

WESTPORT, Mar 03 (Reuters Health) - An outbreak of aseptic meningitis in
northeastern Brazil has been linked to a measles-mumps-rubella (MMR) vaccine
used in a national immunization program.

Such outbreaks could have an impact on public health by influencing the
public's willingness to undergo vaccination, researchers point out in the
March 1st issue of the American Journal of Epidemiology.

"The issue is not simply whether or not a specific vaccine is associated with
an adverse event, but the extent to which a specific vaccination strategy
influences the visibility of the adverse event despite its confirmed relative
rarity, and hence affects public confidence," writes a multicenter team of
researchers led by Dr. Ines Dourado, of the Universidade Federal da Bahia in
Salvador, Brazil.

In the report, the researchers document the cases of 87 children, ages 1 to
11 years, who presented with aseptic meningitis at a hospital in Salvador
between March and October 1997. Of these, 86% were found to have been
vaccinated with MMR in 1997.

Dr. Dourado's team found that there was a sharp increase in the number of
cases of aseptic meningitis 3 weeks after August 16, 1997, the highly
publicized "national vaccination day" and the start of a mass MMR
immunization campaign. The number remained high over the following 3 weeks,
then gradually declined, "returning to prevaccination figures by the 40th
epidemiologic week."

The researchers "conservatively estimated" that the risk of aseptic
meningitis is about 1 in 14,000 MMR vaccine doses. Even though there was no
virologic confirmation, the findings "suggest a causal link between the MMR
mass immunization campaign and the aseptic meningitis outbreak," Dr. Dourado
and associates state.

Am J Epidemiol 2000;151:524-530.