Advancing functional and systemic integration of HIV prevention into public health systems.

The global HIV response has delivered substantial progress, largely through vertical programmes that created parallel systems of financing, governance, and service delivery. Sustaining these gains requires embedding HIV prevention more fully within routine public health systems, particularly as external funding declines and health priorities evolve. This Series paper examines how the principal functions of HIV prevention-risk-based prioritisation, demand generation, quality service provision, and continuity of use-are grounded in long-standing public health principles and essential functions. By tracing these shared roots, we show that integration is not an abandonment of HIV prevention's distinctive achievements but an evolution towards more coherent and sustainable public health systems. Although integration moves HIV prevention beyond exceptionalist approaches, it should be understood as an advance that reinforces durability and equity rather than a compromise that dilutes past gains. Drawing on literature, expert consultations, and country experiences, we compare HIV prevention functions against frameworks, such as WHO's Essential Public Health Functions. This comparison highlights integration as a technically sound and conceptually coherent path and acknowledges the financial, political, and structural legacies of vertical programming. We conclude that system-level integration can sustain HIV outcomes and strengthen overall health system resilience.