Table 1 Parameters for the transmission model
Parameter | Parameter Source | Model | ||
|---|---|---|---|---|
1 | 2 | 3 | ||
a, proportion progressing directly to disease | A | – | – | 0.0665 |
B | – | – | 0.085* | |
b, proportion entering fast latent state | A | – | 0.086 | – |
B | – | 0.09 | – | |
c, rate of progression to disease from slow latent state (per year) | A | 5.94 × 10−4 | 5.94 × 10− 4 | 3.37 × 10− 3 |
B | 2.01 × 10− 3 | 2.01 × 10− 3 | 3.11 × 10− 3* | |
k, rate of progression to disease from fast latent state (per year) | A | 0.0826 | 0.955 | – |
B | 0.4015 | 4.015 | – | |
e, rate of movement from fast latent state to slow latent state (per year) | A | 0.872 | – | – |
B | 4.015 | – | – | |
q, relative susceptibility to re-infection compared to first infection | 0.5 (To explore the role of re-infection in between model differences we also simulated the model with no re-infection, q = 0) | |||
τ, rate of recovery from TB disease (per year) | 1 (assumes that the average duration of disease is approximately 1 year) | |||
β, number of effective contacts (per year) | Varied to produce different TB incidence | |||
m, rate of TB associated mortality | 0.03 | |||
w, relative risk of progressing to disease following preventive therapy | 0.4 (In the primary analysis, we assume preventive therapy has an efficacy of 60% against disease progression from prior infection. We explored the impact of varying w on the results). | |||