The authors evaluated the use of conditional cash transfers as an HIV and sexually transmitted infection prevention strategy to incentivise safe sex.
An unblinded, individually randomised and controlled trial.
10 villages within the Kilombero/Ulanga districts of the Ifakara Health and Demographic Surveillance System in rural south-west Tanzania.
The authors enrolled 2399 participants, aged 18–30 years, including adult spouses.
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.
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.
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
Existing prevention strategies have had a limited impact on the trajectory of the HIV/AIDS epidemic.
Conditional cash transfers have been used successfully in a variety of settings to promote activities that are beneficial to the participants, such as school participation or health check-ups for children.
This trial asks whether conditional cash transfers can be used to prevent people from engaging in activities that are harmful to themselves and others, such as unsafe sex.
We designed and evaluated a novel intervention that tests for risky sexual behaviour repeatedly over short time intervals, reinforcing learning about safer behaviour with cash transfer incentives conditional on testing negative for a set of curable sexually transmitted infections (STIs).
After 12 months, the results from the adjusted model showed a significant reduction in the combined point prevalence of the four curable STIs tested every 4 months by nucleic acid amplification tests in the group that was eligible for the $20 payments, but no such reduction was found for the group receiving the $10 payments.
The results suggest that conditional cash transfers used to incentivise safer sexual practices are a potentially promising new tool in HIV and STIs 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.
Strengths and limitations of this study
This paper reports the results of a novel approach for HIV and STI prevention.
Our study methodology is rigorous, and the results are likely to advance a global conversation about economic approaches to HIV/STI prevention.
Our main outcome measure is the combined point prevalence of four STIs repeatedly tested by nucleic acid amplification tests over the course of the year and which have been incontrovertibly linked to risky sexual activity. These biological outcomes, however, cannot be used to infer the relative importance of STI treatment seeking behaviour versus other behaviour changes, such as increased condom use or reducing riskiness of partners.
The results reported in this study are limited to a 12-month experiment and cannot address the sustainability of improvements in STI outcomes over a longer period, particularly after the conditional cash transfers have been discontinued.