A Theoretical Framework for Evaluating the Impact of Option B+ on Vertical HIV Transmission in Maputo Province, 2003

The prevention of mother-to-child transmission (HIV) is a persistent public health priority in sub-Saharan Africa. Option B+, which provides lifelong antiretroviral therapy to all pregnant and breastfeeding women living with HIV, was introduced to simplify care. A theoretical model is needed to assess its specific effect on vertical transmission within distinct settings like Maputo Province. This article develops a theoretical framework to evaluate the impact of Option B+ on vertical HIV transmission rates in Maputo Province. Its objective is to construct a model that identifies and links key determinants of transmission reduction. The framework is developed through a synthesis of existing public health theories, including the socio-ecological model and health systems frameworks. It integrates concepts from implementation science to map the causal pathways through which Option B+ influences clinical and community-level outcomes. Key insights: The framework posits that the success of Option B+ is contingent upon high levels of maternal retention in care. It hypothesises that a primary mechanism for reducing transmission is sustained viral suppression, which is modelled as directly proportional to the completeness of the treatment cascade. Stigma is identified as a central barrier influencing multiple stages of the care pathway. The proposed theoretical framework offers a structured, multi-level approach for understanding how Option B+ functions within a specific provincial context. It elucidates the underlying processes and contextual factors that determine programme effectiveness beyond simple outcome measurement. Future research should apply this framework to design mixed-methods evaluations in Maputo Province. Programme planners should use the model to identify and strengthen weak components in the PMTCT cascade. Option B+, PMTCT, theoretical framework, vertical transmission, health systems, implementation science. This work provides a conceptual model for systematically analysing the pathways to success or failure of Option B+ programmes, aiming to inform more effective evaluation and implementation in similar contexts.