Vaccine
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The objectives of surveillance for vaccine preventable disease vary with the stage of the vaccination programme. Pre-implementation data is required to estimate the burden of disease and to decide on the appropriate vaccination strategy. Post-implementation data is required to monitor effectiveness but when high coverage is achieved surveillance must be able to accurately identify remaining pockets of susceptible persons. ⋯ Where the incidence is low, however, this approach, will be very expensive. Surveillance of vaccine preventable disease therefore requires flexible surveillance systems which are able to adapt to changes in incidence of infection and in control policy. The use of multiple data sources and supportive information from special studies is essential for the valid interpretation of routine data.