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Lauren Childs, Virginia Tech, Modeling the waning and boosting of immunity: A case study of pertussis in Sweden
January 27, 2020 | 4:15 pm - 5:15 pm EST
Pertussis, commonly known as whooping cough, is caused by the bacterial pathogen Bordetella pertussis. Completely susceptible individuals experience severe disease, with the hallmark whooping cough, but those with partial immunity have milder, if any symptoms. Immunity following natural infection (or immunization) may wane, increasing susceptibility with time since exposure. In this talk, we begin by examining a classic model of waning and boosting immunity with a focus on the bifurcation structure and how this changes as reinfection is considered. Then, we will discuss an extension of this framework with an age- and immune status-dependent model of pertussis transmission. In this model, susceptibility, infectiousness, and symptom severity all vary with immune status, while age affects contacts and vaccination. Using demographic and vaccination data from Sweden and contact data from Finland, we examine age-specific incidence and prevalence and find vaccination leads to a resurgence of immunity-modified pertussis in older children, as observed with effective vaccination programs. In Sweden, substantial subject-matter expertise together with enhanced pertussis surveillance led to an effective vaccination schedule. With data from other locations, such as countries with vastly different demographics, our model may assist in the development and optimization of vaccination schedules for pertussis. This is important to mitigate resurgence of immunity-modified disease due to natural boosting.