The role of seroepidemiology in the comprehensive surveillance of vaccine-preventable diseases.

E70 CMAJ, January 10, 2012, 184(1) © 2012 Canadian Medical Association or its licensors Serological surveillance (serosurveillance) provides estimates of population-level immunity against vaccine-preventable diseases using cross-sectional studies of antibody prevalence. Seroepidemiology is important for evaluating the impact of vaccination programs, as these programs change the immunity of populations, both vaccinated and unvaccinated. Seroepidemiology networks test sera from multiple jurisdictions to estimate ageand sexspecific seroprevalences for specific regions. Despite a strong evidence-based immunization policy, Canada does not have a seroepidemiology network to measure the impact of its vaccination programs. Evidence-informed vaccination policy is more important than ever when one considers the rising costs of new vaccines, waning immunity against select vaccine-preventable diseases, increasing numbers of new Canadians who may be susceptible to vaccine-preventable diseases and an aging population whose immune response following vaccination is less predictable. The monitoring of vaccine-preventable disease in Canada currently consists of surveillance of reportable diseases, adverse events following immunization and immunization coverage. Notifications of reportable disease are important for monitoring trends and detecting outbreaks, but they are known to underestimate incidence and provide little information about the probability of future outbreaks. When combined with mathematical modeling, seroepidemiologic data can show the gradual accumulation of susceptible people, changes in the age-specific risk of infection and the potential for outbreaks. This data can be used to evaluate the impact of vaccination programs and inform decisions concerning vaccine policy, including establishing “catch-up” vaccination programs to help mitigate the risk of outbreaks. National serosurveillance programs are wellestablished in many countries (Table 1). The European seroepidemiology program coordinates serosurveillance across 18 European countries despite national differences in methods for serum collection, disease epidemiology and immunization schedules. Although the Canadian Health Measures Survey will examine the seroprevalence of viral hepatitis, a comprehensive approach to the seroepidemiology of vaccinepreventable diseases does not exist in Canada. This review describes the rationale for establishing a seroepidemiology network in Canada.