Pertussis vaccines have been used in Australia for more than half a century, but despite best efforts disease control remains elusive. Australia is one of several countries with sustained high vaccine coverage to have recently experienced pertussis resurgence, with associated infant morbidity and mortality. Public health responses to date have included reinforcement of the early life vaccination schedule, and third trimester immunization of pregnant women to ensure babies have pertussis antibodies on board at birth.
Multiple explanations have been proposed for the increase in pertussis disease. In truth, there are likely multiple contributing factors, resulting in a ‘perfect storm’. Mathematical and computational models provide a useful framework to explore these interactions, and assess their implications for epidemiology and disease control.
We have used age-structured compartmental models to look back, to understand the way in which changes in vaccine uptake, scheduling and formulation have influenced long term trends in pertussis disease in Australia. Insights gained from these models have enabled us to predict the likely relative benefits of proposed changes to the routine early childhood immunisation schedule, supporting reintroduction of the 18-month booster dose in 2016.
In addition, we have used household-structured individual-based models to look forward, to consider optimal strategic implementation of antenatal vaccination beyond the current emergency response phase. The ability of these models to capture different population characteristics and demographics has additionally allowed us to consider the likely applicability and impact of antenatal vaccine approaches in low and middle income country settings.
Pertussis will be with us for the foreseeable future. Models provide a platform to inform development of efficient and effective strategies for vaccine use, to minimize the burden of pertussis disease.