Potential impact on HIV transmission of a rectal microbicide used by men who have sex with men in southern India

1. Potential impact on HIV transmission of a rectal microbicide used by men who have sex with men in southern India AM Foss, HC Johnson, HJ Prudden, JR Williams, AE Phillips, BM Ramesh, R Washington, M-C Boily, PT Vickermanand CH Watts Anna.Foss@lshtm.ac.uk

2. Aim and objectives Aim: Model the potential impact of a rectal microbicide on the HIV epidemic among MSM in Bangalore, India Objectives: • Project model-estimated future HIV epidemic trends among MSM in Bangalore • Estimate the potential impact of rectal microbicide use by MSM on the HIV epidemic among MSM in Bangalore • Investigate the potential impact of rectal microbicide use by MSM among long-term female partners of MSM • Explore the effect of possible condom substitution

3. Model components A deterministic compartmental model was developed which: simulates joint transmission dynamics of HIV, genital herpes and syphilis incorporates 3 behavioural subgroups of MSM is parameterised and fitted to setting-specific data is coupled with a simple risk equation to estimate infections averted among long-term female partners of MSM Panthi/Bisexual Kothi/Hijra Predominantly insertive Predominantly receptive Versatile Double Decker

4. Key model parameter input estimates for main illustrative fit Random sampling techniques, adjusting for known biases, were used to generate 100,000 different combinations of parameter values (based primarily on data collected as part of the monitoring and evaluation of Avahan, the India AIDS initiative, funded by the Bill & Melinda Gates Foundation (2005)), with the parameter set from the main illustrative fit shown here.

5. Prevalence data and main illustrative fit Adapted from data collected as part of the monitoring and evaluation of Avahan, the India AIDS initiative, funded by the Bill & Melinda Gates Foundation (2005), and data from the National AIDS Control Organisation (2005)

6. Preliminary model projections using main illustrative fit: potential impact if 30% of MSM have access to microbicide and no condom substitution (2010-2015) Consistency of microbicide use in non-condom protected MSM sex acts amongst reached MSM: Condom used with same consistency after microbicide introduction as before (60%)

7. Preliminary model projections using main illustrative fit: potential impact if 30% of MSM have access to microbicide and 20% condom substitution (2010-2015) Consistency of microbicide use in non-condom protected MSM sex acts amongst reached MSM: Condom used in 20% fewer MSM sex acts after microbicide introduction (relative reduction)

8. Potential indirect impact among wives / cohabiting female partners • If condom use among MSM remains the same after microbicide distribution to 30% of MSM, then the percentage of HIV infections averted among their long-term female partners is predicted to be in the range: 2-9% over the 5-year intervention timeframe (using main illustrative fit)

9. Potential indirect impact among wives / cohabiting female partners of MSM (using alternative illustrative fit and assuming 80% of MSM access microbicide of 35% efficacy and use in all non-condom-protected sex, allowing 20% condom substitution)

10. Comparisons across Bangalore and Lima: key conclusions • A 60% efficacious microbicide accessed by 30% of MSM and used in half of non-condom-protected sex acts could avert over 12% of HIV infections among MSM in both settings over 5 years, if condom use remains at pre-microbicide levels • If 20% fewer MSM sex acts are condom-protected after microbicide introduction, then impact lessens, and HIV infections may actually increase • This study highlights the importance of pursuing further research and investment for developing rectal microbicides, and vaginal microbicides for the female partners of MSM • The public health benefit from an effective rectal microbicide could be considerable if used consistently, but condom use must be maintained in order to avoid potentially increasing risk

11. Next steps • Hypothesis testing during fitting procedure to explore further the potential biases in the data samples • Conduct a more rigorous full uncertainty analysis in which additional model fits to the data will be identified • Conduct a multivariate sensitivity analysis to investigate the sensitivity of findings to key assumptions and explore the robustness of the conclusions • Explore whether it is important for models to incorporate behavioural heterogeneity among MSM in order to better predict the HIV epidemic and estimate the potential impact of interventions

12. Acknowledgements • Funders: • Support for this research and conference attendance has been provided by amfAR and the Wellcome Trust • Microbicides Development Programme (MDP), funded by DFID and MRC • Some authors/coauthors are also members of DFID-funded RPC • Collaborators: • London School of Hygiene & Tropical Medicine, UK • Imperial College London, UK • Karnataka Health Promotion Trust, Bangalore, India • St John's Research Institute, Bangalore, India • University of Manitoba, Winnipeg, Canada • Advisory Group: • Catherine Lowndes • Stephen Moses • Michel Alary • Jan Bradley • Robert Lorway • John Anthony • Rex Watts • KaveriGurav