A deterministic, age-structured model of typhoid transmission was fitted to the annual incidence rates of Dong Thap, Vietnam and Kolkata, India via a Markov Chain Monte Carlo. The model includes both person-to-person and water-to-person transmission routes. The model can be used to estimate the long-term impact of the vaccine.
Model name: Typhoid Fever model
Modellers: Virginia Pitzer
We predict vaccine impact on typhoid incidence using a deterministic transmission dynamic model. The model accounts for important features of typhoid epidemiology, e.g. immunity to clinical versus subclinical infection, and the prevalence and contribution of chronic carriers to transmission. We do not distinguish between short- versus long-cycle (i.e. water-borne) transmission because these two transmission routes are not identifiable from the annual incidence estimates used for model fitting, and the bacteria are short-lived in the environment. Dynamic model output on the incidence rate of typhoid fever (per 100,000 person-years) is multiplied by the country-specific demography to produce final estimates.