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22-11-2011 | General practice | Article

Canada needs comprehensive serosurveillance system


Free abstract

MedWire News: Canada lacks a comprehensive surveillance system for vaccine-preventable disease, according to a recent review.

Given the country's range of immunization schedules, its diverse and growing population of new Canadians, and its history of evidence-based immunization policies, Canada "would benefit from a seroepidemiology network," according to researchers.

Publishing their report in the Canadian Medical Association Journal, Sarah Wilson (Ontario Agency from Health Protection, and Promotion, Toronto) and colleagues say that an evidence-informed vaccination policy is critical given the rising costs of new vaccines and the waning immunity against select vaccine-preventable diseases.

Serologic surveillance, or serosurveillance, estimates immunity against vaccine-preventable diseases at the population level using use 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," write Wilson and colleagues.

In Canada, the monitoring of vaccine-preventable disease consists of reportable diseases, adverse events following immunization, and immunization coverage. This system, however, underestimates incidence and does not provide much information about the potential of outbreaks.

Serosurveillance programs are well-established in several European countries, including the UK and the Netherlands, as well as in the USA and Australia.

These systems combine mathematical modeling with epidemiologic data to highlight the gradual accumulation of susceptible individuals, changes in the risk for infection, and the potential for outbreaks.

"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," explain the researchers.

In Canada, there are 13 distinct immunization programs that differ by province and territory, and these programs document vaccine coverage differently.

Importantly, more than 250,000 newcomers arrive in Canada each year, and half of these individuals arrive from countries with no vaccination programs for rubella or mumps. In addition, Canada has a large Aboriginal population and their susceptibility to vaccine-preventable disease may differ from the general population.

The researchers accept that developing a seroepidemiologic network is "ambitious" and would provide challenges related to funding and ethics, as well epidemiologic and laboratory challenges.

"However, these challenges are not insurmountable, and there will always be competing priorities for scarce resources," argue Wilson and colleagues.

They add that if a Canadian serosurveillance network was established, the roles and responsibilities of stakeholders at the federal and provincial level would need to be clarified.

By MedWire Reporters

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