Estimation and management of pandemic influenza transmission risk at mass immunization clinics

Mass immunization clinics (MICs) have become an essential component of pandemic influenza response strategies. By deploying large volumes of vaccines at centralized locations, public health authorities can reduce the complexity of emergency vaccine distribution while also enabling rapid, large-scale vaccination. The risk of influenza transmission at MICs must be understood and mitigated to maximize their effectiveness. We have developed a discrete-event simulation of an MIC that can estimate the expected number of infections resulting from disease transmission within the facility. A simulation experiment is conducted that varies MIC crowdedness, staffing levels and the percentage of infectious individuals entering the MIC-symptomatic or not-to assess the impact of these factors on expected infections. It is shown that the number of expected infections occurring in the MIC, though a small fraction of the influenza cases likely averted due to vaccination, is large enough to warrant mitigation measures.