Pre-Exposure Prophylaxis Reduces HIV Test Positivity Among Men Who Have Sex with Men in Kazakhstan: An Interrupted Time Series Analysis

Abstract Background Eastern Europe and Central Asia faces an accelerating HIV epidemic among gay, bisexual, and other men who have sex with men (GBMSM), yet population-level effectiveness data for pre-exposure prophylaxis (PrEP) remain limited. In May 2021, Kazakhstan implemented a national PrEP programme for GBMSM. Methods We conducted interrupted time series (ITS) analysis of national HIV surveillance data from January 2020 through December 2024 (n = 60 months). The primary outcome was monthly HIV test positivity rate among GBMSM at substantial risk. Standard segmented regression was used to test for immediate and slope changes. We also performed counterfactual analysis to test the cumulative effects against projected pre-intervention trends. Sensitivity analyses controlled for testing volume and examined alternative outcomes. Results By December 2024, the programme achieved 20.1% coverage (1,936 of 9,630 GBMSM at substantial risk). Counterfactual analysis demonstrated significant cumulative reduction in monthly HIV test positivity (mean monthly divergence from projected trends: 0.537 percentage points, 95% CI: 0.393–0.681, p < 0.001). Descriptive comparison showed a 25.7% relative reduction from 3.38% to 2.51%. Effects accumulated gradually over the implementation period rather than as an immediate step-change. Findings remained robust after controlling for a 96% increase in testing volume and across alternative outcomes. Assuming 86% real-world effectiveness (from meta-analyses), the programme currently prevents an estimated 146 HIV infections annually, with a number needed to treat of 13. Conclusions Kazakhstan's PrEP programme demonstrates significant, robust population-level impact on HIV test positivity among GBMSM (25.7% reduction, p < 0.001). The programme currently prevents an estimated 146 infections annually (NNT = 13), with potential to prevent 510 infections annually at 70% coverage. This study provides quasi-experimental evidence for PrEP effectiveness in Kazakhstan, demonstrating that biomedical prevention can achieve measurable population-level impact in concentrated epidemics.