Print PageAge specific differences in transmission and contact rate can strongly influence the speed and magnitude of outbreaks of infections disease. The predictions of reactive outbreak response strategies (e.g. vaccination, school closure, movement restrictions) are highly dependent on the underlying assumptions about the distribution of contacts and transmissibility and susceptibility within the population. Though predictions of the impact of age-targeted strategies are common, empirical tests of these interventions are less common.
Several well-documented, large-scale measles outbreaks over the last decade provide an opportunity to study both age-specific transmission and the impact of age-specific interventions. We use line-listed records from 4 large measles outbreak in Niger, Tchad, Democratic Republic of Congo, and Malawi to assess age-specific patterns and the impact of reactive vaccination campaigns.
Results/Conclusions
We show that the correlation in the epidemic time-series among age classes in consistent with weakly assortative mixing. Using both analyses of transmission before and after specific campaigns we show that age targeted vaccination in these contexts has the potential to hasten the end of the epidemic in the targeted age groups, but had minimal impact on the spread of the epidemic in non-target age classes. We further explore these empirical observations with simulation models to address both potential impacts of age-targeted vaccination on non-target age classes in the context of epidemic response and the sensitivity of non-target age classes to age-targeted intervention under different assumptions of age-structured mixing.
