To analyse the completeness of the COVID-19 vaccination schedule and identify factors associated with vaccine uptake.

Cross-sectional study.

Data were collected through face-to-face interviews conducted in all 26 Brazilian state capitals and the Federal District between 2022 and 2023, using a sequential sampling approach.

A total of 1392 individuals aged 18 years or older experiencing homelessness for at least 6 months were included.

The primary outcome was the completeness of the COVID-19 vaccination schedule (complete vs incomplete), based on self-reported vaccination status. Secondary analyses examined sociodemographic, institutional and behavioural factors associated with vaccine uptake using binary logistic regression.

Completion of the vaccination schedule was positively associated with receiving government aid (OR: 1.58; 95% CI 1.09 to 2.30), visits from street clinic health agents (OR: 3.19; 95% CI 1.95 to 5.36), prior COVID-19 diagnosis (OR: 5.77; 95% CI 3.17 to 11.15), support for mandatory vaccination (OR: 3.76; 95% CI 2.48 to 5.76), trust in vaccine efficacy (OR: 3.92; 95% CI 2.63 to 5.89), seeking information from community sources (OR: 1.91; 95% CI 1.01 to 3.88) and trust in federal authorities (OR: 1.57; 95% CI 1.06 to 2.31).

This study identified structural, social and individual factors associated with complete COVID-19 vaccination among people experiencing homelessness in Brazil. Although overall coverage was substantial, gaps in vaccination completeness persisted. Social support, healthcare outreach and trust in vaccines were associated with higher uptake, highlighting important barriers and facilitators to vaccination in socially vulnerable populations.

Hypertensive disorders of pregnancy, such as pre-eclampsia (PE), are one of the leading causes of maternal and perinatal deaths in low- and middle-income countries (LMICs). Although clinical practice guidelines (CPGs) for PE prevention and management are available, there is limited information on their implementation in LMIC contexts. This realist synthesis therefore aims to uncover the causal explanations underpinning the implementation of CPG recommendations for PE prevention and management in Eastern, Central and Southern African contexts. By developing and refining initial programme theories (IPTs), we will generate a pragmatic evidence base explaining how contextual factors trigger mechanisms that lead to intended and unintended outcomes and why implementation varies across the different settings.

We conceptualise the implementation of CPGs for PE prevention and management as complex social interventions operating within complex adaptive systems. The realist synthesis method will be employed to systematically review the literature for evidence synthesis. The review process will be conducted in five phases, each iteratively building on the previous phase to uncover generative causation and refine the IPTs. We will identify articles through iterative purposive searching in six electronic databases and search engines (Google Scholar, PubMed, Cochrane, MEDLINE, EMBASE Global Health) and through screening WHO sources. Advisory group consultations will be held to formulate, prioritise and refine IPTs. To conceptualise our realist theories through generative causation, we will analyse the data using a retroductive approach, an integration of inductive, deductive and abductive reasoning. We will inductively examine theoretical insights related to five established care moments and explore how CPGs operate during these moments, including where and how they fail to work as intended. The five care moments are: (1) Risk assessment/prevention, (2) Diagnosing disease, (3) Management of PE without severe features, (4) With severe features and (5) Decision making around birth. Deductive reasoning will support sense-making of evidence-based theories through the lens of theories that have been used to explain the adoption of guidelines in healthcare settings. Lastly, abductive reasoning, centring researcher hunches, will help to unearth mechanisms that have been insufficiently detailed in the literature. The intervention-context-actor-mechanism-outcome heuristic will be used to configure programme theories and articulate the theories using the if-then statements.

This project is part of the larger PREvention of Severe Hypertensive Adverse events (PRESHA) project, which aims to improve the detection, prevention and management of PE in Tanzania. PRESHA has ethical clearance from the Regional Ethics Board in Norway and the National Health Research Ethics Committee in Tanzania. Findings of the review will support the contextual development of CPGs for the prevention and management of PE, which will be implemented within the context of the PRESHA trial.