In short, the reinfection rate was assumed to be 30% of the original infection rate.
Additional information:
In HEP-SIM model, there are two types of infections: first time infection from susceptible population and reinfection from cured population.
First, each individual in susceptible population can be newly infected with HCV and the number of new infections every year is determined by the following equation:
Number of infections = S α (I+D/N)
where α is the infection rate, S indicates the susceptible population size, I indicates the infected but diagnosed population size, D indicates the infected and diagnosed population size, and N is the total population size. In fact, (I+D/N) represents the chronic HCV prevalence in a given year.
Second, each individual in cured population can be reinfected with HCV and the number of new reinfections every year is determined by the following equation
Number of refinections= R 𝛿 α (I+D/N)
where (I+D/N) indicates the prevalence of chronic HCV, R indicates the cured population size, and 𝛿 is weight parameter to modify the infection rate α. Since cured patients might be more cautious and have less risky behaviors, we assumed 𝛿 ∈ (0,1). Therefore, reinfection rate, denoted by 𝛿 α, is smaller than the original infection rate α.
In the case of HCV elimination tool, we assumed 𝛿 = 0.3.