What is the achievable effectiveness of the India AIDS Initiative intervention among female sex workers under target coverage? Model projections from southern India
- J R Williams1,
- A M Foss2,
- P Vickerman2,
- C Watts2,
- B M Ramesh3,
- S Reza-Paul3,4,
- R G Washington4,5,
- S Moses4,
- J Blanchard4,
- C M Lowndes2,6,
- M Alary7,
- M-C Boily1
- 1Department of Infectious Disease Epidemiology, Imperial College London, St Mary’s Hospital, Norfolk Place, London W2 1PG, UK
- 2London School of Hygiene and Tropical Medicine, London, UK
- 3Karnataka Health Promotion Trust, India
- 4Departments of Medical Microbiology, Community Health Sciences and Medicine, University of Manitoba, Winnipeg, Canada
- 5Institute of Population Health and Clinical Research, St John’s National Academy of Health Sciences, India
- 6Health Protection Agency, UK
- 7Population Health Research Unit, Centre hospitalier affilié universitaire de Québec and Université Laval, Québec, Canada
- Correspondence to: Mare-Claude Boily Department of Infectious Disease Epidemiology, Imperial College London, St Mary’s Hospital, Norfolk Place, London W2 1PG, UK;
- Accepted 7 July 2006
Background: The India AIDS Initiative (Avahan) prevention programme funded by the Bill and Melinda Gates Foundation aims to reduce HIV prevalence in high risk groups such as female and male sex workers and their clients, to limit HIV transmission in the general population.
Objectives: To assess the potential effectiveness of the Avahan intervention at the level of coverage targeted, in different epidemiological settings in India.
Methods: A deterministic compartmental model of the transmission dynamics of HIV and two sexually transmitted infections, and sensitivity analysis techniques, were used, in combination with available behavioural and epidemiological data from Mysore and Bagalkot districts in the Indian state of Karnataka, to evaluate the syndromic sexually transmitted infection (STI) management (STI treatment), periodic presumptive treatment of STI (PPT), and condom components of the Avahan intervention targeted to female sex workers (FSW).
Results: If all components of the intervention reach target coverage (that is, PPT, STI treatment and condom use), the intervention is expected to prevent 22–35% of all new HIV infections in FSW and in the total population over 5 years in a low transmission setting like Mysore, and to be half as effective in high transmission settings such as Bagalkot. The results were sensitive to small variations in intervention coverage. The condom component alone is expected to prevent around 20% of all new HIV infections over 5 years in Mysore and around 6% for the STI component alone; compared with 7%–14% for the PPT component alone. Multivariate sensitivity analyses suggested that interventions may be more effective in settings with low FSW HIV prevalence and small FSW populations, whereas HIV prevalence was most influenced by sexual behaviour and condom use parameters for FSW.
Conclusion: The Avahan intervention is expected to be effective. However, to be able to demonstrate effectiveness empirically in the different settings, it is important to achieve target coverage or higher, which in the case of PPT could take a number of years to achieve. These preliminary model predictions need to be validated with more detailed mathematical models, as better data on sexual behaviour, condom use, STI and HIV trends over time, and intervention coverage data accumulate over the course of the programme.
- ART, antiretroviral therapy
- CSW, commercial sex workers
- CT, Chlamydia trachomatis
- FSW, female sex workers
- GC, Neisseria gonorrhoeae
- HSV, herpes simplex virus
- IBBA, Integrated Biological and Behavioural Assessment
- ICHAP, India-Canada Collaborative HIV/AIDS Project
- MSM, men who have sex with men
- PF, prevented fraction
- PPT, periodic presumptive treatment
- STI, sexually transmitted infections
↵* In general the user can specify the rate of change of sexual partners corresponding to different sexual activities and the average number of sex acts per unit time for each type of partnership.