The household has long been recognised as a key focus of infection transmission. Hope-Simpson described a four-fold risk of ‘Hong Kong’ influenza, the 1968 pandemic strain, among family members of an affected case. More recent observations of seasonal and pandemic influenza spread have confirmed these risks, which are particularly pronounced when children are primary cases or contacts. Family size and composition have long been known to influence infants’ risk of infection exposure, with observations from the 1950s demonstrating increased likelihood of bacterial meningitis among babies with a school-aged sibling. In situations where mass immunisation results in reduced pathogen circulation, with waning immunity, opportunities for boosting may depend critically on the evolving age composition and social interactions of households of a particular type.
This project involves the development and application of a novel agent-based model framework that captures realistic age and household structure over periods of demographic change. This framework is being used to consider the longevity of vaccine protection within households and at population level over the years following vaccine introduction.