Vaccinating Youth in Tropics to Protect Elderly

A model suggests that vaccinating children and teens against the flu can help protect the elderly in tropical countries. Influenza kills up to 650,000 people worldwide every year. In part due to the lack of strong seasonality and differences in vaccine supply, optimal vaccination strategies for the tropics may differ from those in temperate zones. Joseph Servadio and colleagues parameterized an age-structured mathematical model of influenza transmission to the asynchronous, non-annual epidemiology of tropical influenza in Vietnam, a country with low vaccine coverage. The model includes three subtypes of the flu virus. Vaccinating year-round was found to be more effective than vaccinating all at once. Focusing vaccination effort on young people ages 10–19, a group who are especially likely to transmit the virus, was the best strategy for most vaccine supply scenarios, but remaining vaccine doses must be carefully allocated to other age groups—particularly those over 60 years of age—to minimize mortality. The scarcer the vaccines, the more crucial age-specific allocation is to keeping death rates low. When vaccine supplies are limited, the authors advocate for allocating vaccines to school-age children and elderly adults.