Because transmission occurs at variable rates, exposure risk even within the known geographic areas of meningococcal disease activity can be very difficult to predict. The place and duration of exposure are not the only factors to consider. Climatic conditions, which vary from year to year, have a major impact on the intensity of risk. The setting of exposure, such as crowded, intimate or institutional living quarters within a disease activity area is also important. In addition, the health status of the traveller must be considered.
Age is a major determinant of disease risk.
A history of splenectomy and compromised immune function are also important risk factors. The epidemiologic pattern of meningococcal infection in developing nations where the disease is active indicates that children are at the greatest risk of disease and that the peak incidence may occur in those under 2 years of age. Disease occurrence in these areas is seasonal and can greatly exceed that found in other parts of the world. Before recommending vaccination against meningococcal disease, the physician must exercise considerable clinical judgement in the assessment of the international traveller, taking into account potential geographic exposure, health status and planned activities. The meningococcal polysaccharide vaccines licensed in Canada are safe, immunogenic and include the serogroups A and C, which are most commonly associated with epidemics of the disease.