Table 1

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

ParameterBaseline valueSource
 Duration of untreated urogenital infection (males and females), months1227
 Duration of untreated anorectal infection (females), months1228
 Transmission probability per vaginal sex actCalibrated
 Transmission probability per anal sex actCalibrated 
 Daily autoinoculation probabilityCalibrated 
 Frequency of unprotected vaginal sex acts, per week229
 Frequency of unprotected anal sex, per week0.529*
 Number of partners, per year†3STI clinic‡
 Fraction of people in a partnership at any time,%†66STI clinic‡
 Anal sex past six months, %§18STI clinic¶
Intervention parameters
 Azithromycin effectiveness** urogenital infection, %94.330
 Doxycycline effectiveness** urogenital infection, %97.130
 Azithromycin effectiveness** anorectal infection, %82.911
 Doxycycline effectiveness** anorectal infection, %99.611
 Female testing uptake, % per year1415
 Period of recent anal sex to determine which treatment to provide, months617
 Partner notification probability0.516
  • *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.