Parameters of the model and corresponding values reflecting a heterosexual population of men and women aged 15–29 years visiting STI clinics (excluding swingers and prostitutes) receiving the standard of care
| Parameter | Baseline value | Source |
|---|---|---|
| Infection | ||
| Duration of untreated urogenital infection (males and females), months | 12 | 27 |
| Duration of untreated anorectal infection (females), months | 12 | 28 |
| Transmission | ||
| Transmission probability per vaginal sex act | Calibrated | |
| Transmission probability per anal sex act | Calibrated | |
| Daily autoinoculation probability | Calibrated | |
| Behaviour | ||
| Frequency of unprotected vaginal sex acts, per week | 2 | 29 |
| Frequency of unprotected anal sex, per week | 0.5 | 29* |
| Number of partners, per year† | 3 | STI clinic‡ |
| Fraction of people in a partnership at any time,%† | 66 | STI clinic‡ |
| Anal sex past six months, %§ | 18 | STI clinic¶ |
| Intervention parameters | ||
| Azithromycin effectiveness** urogenital infection, % | 94.3 | 30 |
| Doxycycline effectiveness** urogenital infection, % | 97.1 | 30 |
| Azithromycin effectiveness** anorectal infection, % | 82.9 | 11 |
| Doxycycline effectiveness** anorectal infection, % | 99.6 | 11 |
| Female testing uptake, % per year | 14 | 15 |
| Period of recent anal sex to determine which treatment to provide, months | 6 | 17 |
| Partner notification probability | 0.5 | 16 |
*Data of heterosexuals are lacking, so value was taken from young men who having sex with other men.
†These parameters are used to estimate the yearly pair formation and separation rates. Only number of partners in the last half year is routinely collected. The median number (two partners per year) is used and transferred to partners per year by multiplying by 1.5.
‡Routinely collected data of heterosexual STI clinic attendees (men and women) aged 15–29 years in South Limburg, the Netherlands, between 2006 and 2013.
§In the model, this parameter is decomposed in a fraction of people that prefers anal sex (40%) and a probability of anal sex in partnerships where one person wants anal sex and the other one not (15%).
¶Data of female STI clinic attendees aged 18–29 years in South Limburg, the Netherlands, who were included in the study on routine universal anorectal testing.
**Effectiveness is defined in the model as the percentage of people that are susceptible again after treatment.