Introduction
HIV infections
HIV INFECTIONS
Increases in the availability and uptake of antiretroviral therapy (ART), including under guidelines of universal ART for pregnant and breastfeeding women, have led to massive reductions in new paediatric HIV infections [An approach which has been posited to reduce disengagement from care is the integration of HIV care into other routine health services, although the current evidence for effectiveness is mixed [Given the promise of this model of care for postpartum women, there is a need to refine and target future implementation of this intervention. Critical to this refinement is the identification of factors that may modify intervention effects, and an exploration of mechanisms of change. A framework that may be beneficial to this is Social Action Theory (SAT). SAT delineates a model of contextual determinants as well as social interaction and individual self-regulatory processes, and the mechanisms by which these lead to health behaviours [Following the conclusion of the MCH-ART randomised controlled trial, our aim here was to quantitatively examine (i) psychosocial modifiers of the intervention effect and (ii) potential mediators of the effect. The goal of examining modifiers was to identify groups for whom the intervention was most beneficial and to whom the intervention could be targeted, as well as groups for whom the intervention was not effective and that warrant further attention in intervention development. In parallel, the goal of examining mediators was to understand how integrated services lead to improved outcomes, with a view to refining interventions by identifying the most effective components.