Objective: To determine the incidence of severe adverse events temporally associated with meningococcal vaccines administered as part of a mass vaccination program.
Design: Retrospective descriptive study of events reported to a passive provincial surveillance system.
Setting: The province of Quebec.
Participants: The 1,198,751 individuals aged 6 months to 20 years who were vaccinated against meningococcal disease between Dec. 27, 1992, and Mar. 31, 1993.
Outcome measures: Total numbers and rates of severe adverse events, including allergic reactions, anaphylactic reactions, neurological events (other than abnormal crying and screaming) and other serious or unusual events.
Results: A total of 118 reports of severe adverse events were selected from the surveillance system. The most frequent were allergic reactions (9.2 per 100,000 doses). Few anaphylactic or neurologic reactions were reported (0.1 and 0.5 per 100,000 doses respectively). There were no reports of sequelae or of encephalopathy, meningitis or encephalitis.
Conclusion: Meningococcal vaccines seem to be associated with fewer adverse events than have previously been reported. Existing surveillance programs are useful for determining the incidence of adverse events temporally associated with vaccines.