Population-level impact of Avahan in Karnataka state, south India using multilevel statistical modelling techniques

To assess the population-level impact of "Avahan," the India AIDS Initiative of the Bill & Melinda Gates Foundation, between 2003 and 2008 in Karnataka state, India.

Secondary data analysis using all consistent data collection sites from antenatal clinic (ANC) sentinel surveillance data from 2003 to 2008 in Karnataka.

A multilevel logistic regression model considering individual- and district-level variables was developed to compare time trends in HIV prevalence among young ANC women (younger than 25 years of age) between Avahan (18) and non-Avahan (9) districts. District-level random effects were considered for the intercept and time. The impact was assessed using interaction terms between district type (Avahan vs. non-Avahan) and time. The number of cases averted was estimated, comparing predicted ANC HIV prevalence in the presence versus the absence of Avahan. Data from the National Family Health Survey Round 3 (2006) were used to extrapolate these numbers to the general population.

HIV prevalence among young ANC women declined from 1.46% (2003) to 0.83% (2008). The HIV prevalence trend was significantly different between Avahan and non-Avahan districts (P = 0.046). Overall, 87,035 cases of HIV infection were estimated to have been averted in the Karnataka general population because of Avahan during the 2003-2008 period (range under varying assumptions: 55,160-150,784).

Our results suggest that Avahan has had a significant impact on the HIV epidemic in the general population of Karnataka. These results suggest that targeted interventions similar to Avahan should be implemented and scaled up in all concentrated and mixed HIV epidemics.