Article Text

Incentivising safe sex: a randomised trial of conditional cash transfers for HIV and sexually transmitted infection prevention in rural Tanzania
  1. Damien de Walque1,
  2. William H Dow2,
  3. Rose Nathan3,
  4. Ramadhani Abdul4,
  5. Faraji Abilahi4,
  6. Erick Gong5,
  7. Zachary Isdahl6,
  8. Julian Jamison7,
  9. Boniphace Jullu4,
  10. Suneeta Krishnan8,
  11. Albert Majura4,
  12. Edward Miguel6,
  13. Jeanne Moncada9,
  14. Sally Mtenga3,
  15. Mathew Alexander Mwanyangala4,
  16. Laura Packel10,
  17. Julius Schachter9,
  18. Kizito Shirima3,
  19. Carol A Medlin11
  1. 1The World Bank, Development Research Group, Washington, District of Columbia, USA
  2. 2School of Public Health, University of California, Berkeley, California, USA
  3. 3Ifakara Health Institute, Dar-es-Salaam, Tanzania
  4. 4Ifakara Health Institute, Ifakara, Tanzania
  5. 5Department of Economics, Middlebury College, Middlebury, Vermont, USA
  6. 6University of California, Berkeley, California, USA
  7. 7Center for Behavioural Economics, Federal Reserve Bank of Boston, Boston, Massachusetts, USA
  8. 8Research Triangle Institute International, Research Triangle Park, North Carolina, USA
  9. 9Department of Laboratory Medicine, University of California, San Francisco, California, USA
  10. 10Global Health Sciences Prevention and Public Health Group, University of California, San Francisco, California, USA
  11. 11Health Economics and Finance, Global Health Program, The Bill and Melinda Gates Foundation, Seattle, Washington, USA
  1. Correspondence to Dr Damien de Walque; ddewalque{at}


Objective The authors evaluated the use of conditional cash transfers as an HIV and sexually transmitted infection prevention strategy to incentivise safe sex.

Design An unblinded, individually randomised and controlled trial.

Setting 10 villages within the Kilombero/Ulanga districts of the Ifakara Health and Demographic Surveillance System in rural south-west Tanzania.

Participants The authors enrolled 2399 participants, aged 18–30 years, including adult spouses.

Interventions Participants were randomly assigned to either a control arm (n=1124) or one of two intervention arms: low-value conditional cash transfer (eligible for $10 per testing round, n=660) and high-value conditional cash transfer (eligible for $20 per testing round, n=615). The authors tested participants every 4 months over a 12-month period for the presence of common sexually transmitted infections. In the intervention arms, conditional cash transfer payments were tied to negative sexually transmitted infection test results. Anyone testing positive for a sexually transmitted infection was offered free treatment, and all received counselling.

Main outcome measures The primary study end point was combined prevalence of the four sexually transmitted infections, which were tested and reported to subjects every 4 months: Chlamydia trachomatis, Neisseria gonorrhoeae, Trichomonas vaginalis and Mycoplasma genitalium. The authors also tested for HIV, herpes simplex virus 2 and syphilis at baseline and month 12.

Results At the end of the 12-month period, for the combined prevalence of any of the four sexually transmitted infections, which were tested and reported every 4 months (C trachomatis, N gonorrhoeae, T vaginalis and M genitalium), unadjusted RR for the high-value conditional cash transfer arm compared to controls was 0.80 (95% CI 0.54 to 1.06) and the adjusted RR was 0.73 (95% CI 0.47 to 0.99). Unadjusted RR for the high-value conditional cash transfer arm compared to the low-value conditional cash transfer arm was 0.76 (95% CI 0.49 to 1.03) and the adjusted RR was 0.69 (95% CI 0.45 to 0.92). No harm was reported.

Conclusions Conditional cash transfers used to incentivise safer sexual practices are a potentially promising new tool in HIV and sexually transmitted infections prevention. Additional larger study would be useful to clarify the effect size, to calibrate the size of the incentive and to determine whether the intervention can be delivered cost effectively.

Trial registration number NCT00922038

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-commercial License, which permits use, distribution, and reproduction in any medium, provided the original work is properly cited, the use is non commercial and is otherwise in compliance with the license. See: and

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  • To cite: de Walque D, Dow WH, Nathan R, et al. Incentivising safe sex: a randomised trial of conditional cash transfers for HIV and sexually transmitted infection prevention in rural Tanzania. BMJ Open 2012;2:e000747. doi:10.1136/bmjopen-2011-000747

  • Funding The study was funded by the World Bank Research Committee, the Spanish Impact Evaluation Fund and the Knowledge for Change Program managed by the World Bank and the William and Flora Hewlett Foundation through the Population Reference Bureau. The study funders had no role in the study design, in the collection, analysis and interpretation of data, in the writing of the report and in the decision to submit the article for publication and researchers were independent from the funders. The findings, interpretations and conclusions expressed in this paper are entirely those of the authors. They do not necessarily represent the views of the International Bank for Reconstruction and Development/World Bank and its affiliated organisations or those of the Executive Directors of the World Bank or the governments they represent.

  • Competing interests None.

  • Patient consent The article does not contain personal medical information about an identifiable living individual.

  • Contributors DdW, WHD, RN and CAM made contributions to each part of the project, planned and designed the study, conducted the analysis, interpreted the findings and contributed to the manuscript. The Ifakara Health Institute was the main implementing agency for the project: BJ and FA managed the Ifakara laboratory testing, AM led field operations, MAM facilitated operations, KS programmed the study systems and together with RA managed the database and SM was responsible for outreach to participating communities and health clinics. EG contributed to data analysis, LP conducted in-depth interviews and ZI was project director onsite in Tanzania. From University of California, San Francisco, JM and JS set up the Ifakara Health Institute laboratory, developed laboratory protocols and were responsible for quality control. SK, JJ and EM as senior investigators have contributed throughout the project and are leading subanalyses linked to the main study in their respective fields of expertise. All authors, external and internal, had full access to all the data (including statistical reports and tables) in the study and can take responsibility for the integrity of the data and the accuracy of the data analysis. DdW and WHD are the guarantors of the study.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement No additional data available.