Parameter Description Baseline value (range) Ref.
  Epidemic parameters (pre-intervention)1:
βm Male HIV acquisition risk per act 0.0038 (0.0021 - 0.0068) [33]
βw Female HIV acquisition risk per act 0.003 (0.0019 - 0.0046) [33]
βr Relative transmissibility of drug-resistant HIV 0.75 (0.5-1) [20]
1/μ Average time to remain sexually active 35 years  (30-40) [34, 44]
dr,d Annual rate of progression to AIDS  for individuals infected with resistant and wild-type HIV 1/10 (1/12-1/7) [45, 46]
nw,nm Average number of sexual acts per year for women and men 70 (60 – 100) [31, 32]
ρwm Average number of sexual partners per year for women and men 1.5 (1-2) [31, 32]
c Rate of condom use in general population 30% (20%-40%) [31, 32]
αc Condom efficacy per act 90% (80-95%) [47]
P HIV-prevalence in absence of PrEP 21% (1-35%) [1]
R0 Basic reproduction number in absence of PrEP 1.27 (1.01- 1.55) calculated
  • Intervention parameters2:
k Fraction of PrEP users among new recruits 60% (40%- 80%) assumed
k1 Initial fraction of the population who decide to use PrEP k (40%- 80%) assumed
σ Fraction of PrEP users with prescription who share their pills with untracted users 10% (0%-20%) assumed
γa Relative PrEP efficacy for sharers 50% (0%- 100%) assumed, [20]
γr Relative PrEP efficacy for users exposed to drug-resistant HIV 25% (0%- 100%) assumed, [20]
αs PrEP efficacy in reducing susceptibility per act 70% (50%- 90%) assumed, [5-7]
αi PrEP efficacy in reducing infectiousness per act 70% (50%- 90%) assumed
re Rate of condom replacement in PrEP users 10% (0%- 20%) assumed
r Annual rate to develop resistance if acquire HIV when using PrEP (perfect adherers) 2 (1- 4) assumed, [20]
r1 Annual rate to develop resistance if acquire HIV when using PrEP (sharers) γar(0-4) assumed
θ  Reduction in the initial fraction of HIV positive individuals who start using PrEP (pre-introduction control) 80% (60- 100%) assumed
1/δ Duration of continuous usage of PrEP after HIV acquisition (prescribed users) 6m  (4m-1y) assumed, [20]
1/δ1M.  Duration of continuous usage of PrEP after HIV acquisition (secondary sharers) 5y  (2y-10y) assumed
τ Annual rate of resistance reversion for infected former PrEP users who developed drug resistance when on PrEP 3 (2- 4) assumed, [20]
τ1 Annual rate of resistance reversion for individuals infected with drug-resistant HIV acquired through transmission 0.25 (0.1- 0.5) assumed, [20]
1Ranges for epidemic parameters are sampled uniformly to obtain parameter sets which are filtered to select 1000 epidemics with R0>1 and HIV prevalence between 1% and 35% in absence of PrEP. 2Ranges for intervention parameters are used in multivariate sensitivity analysis.
Table1: Parameter values and ranges.
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