This is an age-structured transmission dynamic model of serogroup A Neisseria meningitidis (NmA) to investigate the impact of immunisation with MenAfriVac. Individuals may be susceptible, carriers, ill or recovered and in each of these states be vaccinated or unvaccinated, with vaccinated individuals having lower risks of infection (carriage acquisition) and disease. The model captures the key features of meningococcal epidemiology, including seasonality, age-specific carriage and periodic but irregular epidemics. Seasonality is implemented through seasonal forcing of the transmission rate, the extent of which varies stochastically every year.
Model name: MenA model
Modellers: Mike Jackson, Lucy McNamara
Institution: Kaiser Permanente Washington Health Research Institute and Centers for Disease Control and Prevention (CDC)
The model simulates colonization, transmission, and disease of serogroup A Neisseria meningitidis (NmA) in the African meningitis belt. It is a dynamic, discrete-space, discrete-time model, which is a variant of the traditional Susceptible-Infectious-Recovered (SIR) compartmental model. Additional compartments account for differing levels of immunity to colonization and to invasive disease among those colonized. The model is also age-structured. Seasonal forcing of the “who acquires infection from whom” matrix is used to account for the strong seasonality of NmA disease in the meningitis belt. Stochastic variation in transmission is used to reproduce the varying pattern of major epidemics, which occur every 8-12 years and can last across multiple dry seasons.