ABSTRACT
This chapter first outlines the main methods of vaccine-preventable disease surveillance, considering data sources, case definitions, biases and methods for descriptive analyses. These methods are applicable to surveillance at both national and subnational level and are hence also relevant for countries or diseases where national surveillance is lacking. In addition to reducing the incidence of disease, mass vaccination programmes can also impact on the ecology of both targeted and non-targeted micro-organisms. The ecological effects on micro-organisms can include a change in the distribution of subtypes of the pathogen-by-pathogen adaptation and serotype replacement (see Chapter 5). These changes are important to monitor since they necessitate changes in vaccine policy, irrespective of whether the changes are induced by the vaccination programme. In the second section, the chapter provides an overview of methods to monitor changes in pathogen populations.
