Grant MacKenzie of the MRC Unit in The Gambia and colleagues describe in this week's PLoS Medicine how they set up a population-based surveillance system to assess the impact of pneumococcal conjugate vaccines (PCVs) on invasive pneumococcal disease (IPD) and radiological pneumonia in children in The Gambia.

The surveillance system is expected to inform immunisation policy and serves as a potential model for those introducing routine PCV vaccination in diverse settings.

The authors state: "Evidence of sustained reduction of IPD and radiological pneumonia due to PCVs is important to justify their introduction and ongoing use.

Identification of emerging pneumococcal serotypes may also assist the design of future PCVs."