Population-Level Impact of Avahan in Karnataka State, South India Using Multilevel Statistical Modelling Techniques

Increased HIV prevention program coverage and decline in HIV prevalence among female sex workers in south India

BACKGROUND

As one way of assessing the impact of Avahan, the India AIDS Initiative of the Bill & Melinda Gates Foundation, we examined the association between HIV prevention program indicators and changes in HIV prevalence among female sex workers (FSWs) between 2005 and 2009.

METHODS

We conducted a secondary data analysis from 2 large cross-sectional surveys (2005-2006 and 2008-2009) across 24 districts in south India (n = 11,000 per round). A random-effect multilevel logistic regression analysis was performed using HIV as the outcome, with individual independent variables (from both surveys) at level 1 and district-level FSW-specific program indicators and contextual variables at level 2. Program indicators included their 2006 value, the difference in their values between 2008 and 2006, and the interaction between this difference and study round.

RESULTS

HIV prevalence among FSWs decreased from 17.0% to 14.2% (P < 0.001). This decline varied significantly (P = 0.006) across levels of difference in program coverage (% of FSWs contacted by the program in a given year). Odds ratios comparing HIV prevalence between rounds changed with the level of increase in coverage and were statistically significant with coverage increase ≥ quartile (Q) 1: odds ratio, 0.85 at Q1; 0.78 at Q2; 0.66 at Q3; and 0.51 at Q4.

CONCLUSIONS

These findings suggest that increased program coverage was associated with declining HIV prevalence among FSWs covered by the Avahan program. The triangulation of our results with those from other approaches used in evaluating Avahan suggests a major impact of this intervention on the HIV epidemic in southern India.

Two cross-sectional studies in south India assessing the effect of an HIV prevention programme for female sex workers on reducing syphilis among their clients

Objective

To assess the impact of the Avahan HIV prevention programme for female sex workers (FSWs) in south India on reducing syphilis prevalence among their clients, by comparing rates of syphilis over time as reported in two large-scale surveys of FSWs’ clients.

Methods

A random-effect multilevel logistic regression analysis was performed using syphilis as the dependent variable, with individual independent variables (from the two survey rounds) at level 1 and the district-level programme (from the Avahan computerised monitoring and information system) and contextual variables (from Indian government datasets) at level 2. Programme variables included their 2006 value and their difference in value between 2008 and 2006, as well as the interaction between the latter and the study round. The analysis also controlled for baseline syphilis prevalence and its interaction with the study round.

Results

Syphilis decreased significantly among FSWs’ clients, from 4.8% (round 1) to 2.6% (round 2), p<0.001. The OR of the interaction term between the difference in programme coverage of FSWs and the round was 0.98 (p=0.023), suggesting that increased coverage was associated with a reduced incidence of syphilis.

Conclusions

This study suggests that the Avahan intervention programme among FSWs reduced syphilis rates among their clients.

Assessment of the population-level effectiveness of the Avahan HIV-prevention programme in South India: a preplanned, causal-pathway-based modelling analysis

BACKGROUND

Avahan, the India AIDS initiative of the Bill & Melinda Gates Foundation, was a large-scale, targeted HIV prevention intervention. We aimed to assess its overall effectiveness by estimating the number and proportion of HIV infections averted across Avahan districts, following the causal pathway of the intervention.

METHODS

We created a mathematical model of HIV transmission in high-risk groups and the general population using data from serial cross-sectional surveys (integrated behavioural and biological assessments, IBBAs) within a Bayesian framework, which we used to reproduce HIV prevalence trends in female sex workers and their clients, men who have sex with men, and the general population in 24 South Indian districts over the first 4 years (2004-07 or 2005-08 dependent on the district) and the full 10 years (2004-13) of the Avahan programme. We tested whether these prevalence trends were more consistent with self-reported increases in consistent condom use after the implementation of Avahan or with a counterfactual (assuming consistent condom use increased at slower, pre-Avahan rates) using a Bayes factor, which gave a measure of the strength of evidence for the effectiveness estimates. Using regression analysis, we extrapolated the prevention effect in the districts covered by IBBAs to all 69 Avahan districts.

FINDINGS

In 13 of 24 IBBA districts, modelling suggested medium to strong evidence for the large self-reported increase in consistent condom use since Avahan implementation. In the remaining 11 IBBA districts, the evidence was weaker, with consistent condom use generally already high before Avahan began. Roughly 32700 HIV infections (95% credibility interval 17900-61600) were averted over the first 4 years of the programme in the IBBA districts with moderate to strong evidence. Addition of the districts with weaker evidence increased this total to 62800 (32000-118000) averted infections, and extrapolation suggested that 202000 (98300-407000) infections were averted across all 69 Avahan districts in South India, increasing to 606000 (290000-1 193000) over 10 years. Over the first 4 years of the programme 42% of HIV infections were averted, and over 10 years 57% were averted.

INTERPRETATION

This is the first assessment of Avahan to account for the causal pathway of the intervention, that of changing risk behaviours in female sex workers and high-risk men who have sex with men to avert HIV infections in these groups and the general population. The findings suggest that substantial preventive effects can be achieved by targeted behavioural HIV prevention initiatives.

FUNDING

Bill & Melinda Gates Foundation.

Female sex work interventions and changes in HIV and syphilis infection risks from 2003 to 2008 in India: a repeated cross-sectional study

OBJECTIVES

We examined if increased spending and coverage of female sex worker (FSW) interventions were associated with declines in HIV or syphilis risk among young pregnant women (as a proxy for new infections in the general population) in the high-burden southern states of India.

DESIGN

Repeated cross-sectional analysis.

SETTING

We used logistic regression to relate district-level spending, number of sexually transmitted infections (STIs) treated, FSWs reached or condoms distributed to the declines in the annual risk of HIV and syphilis from 2003 to 2008 among prenatal clinic attendees in the four high-HIV burden states of Andhra Pradesh, Karnataka, Maharashtra and Tamil Nadu.

PARTICIPANTS

386 961 pregnant women aged 15-24 years (as a proxy for incident infections in the adult population).

INTERVENTIONS

We examined National AIDS Control Organisation (NACO) data on 868 FSW intervention projects implemented between 1995 and 2008.

PRIMARY AND SECONDARY OUTCOME MEASURES

HIV or syphilis infection.

RESULTS

HIV and syphilis prevalence declined substantially among young pregnant women. Each additional STI treated (per 1000 people) reduced the annual risk of HIV infection by -1.7% (95% CI -3.3 to -0.1) and reduced the annual risk of syphilis infection by -10.9% (95%CI -15.9 to -5.8). Spending, FSWs reached or condoms distributed did not reduce HIV risk, but each was significantly associated with reduced annual risk of syphilis infection. There were no major differences between the NACO-funded and Avahan-funded districts in the annual risk of either STI.

CONCLUSIONS

Targeted FSW interventions are associated with reductions in syphilis risk and STI treatment is associated with reduced HIV risk. Both more and less costly FSW interventions have comparable effectiveness.