Improving childhood vaccination among minority populations in middle- and high-income countries: a realist review of health system interventions

BACKGROUND: Most minority populations in Europe generally exhibit lower childhood vaccine uptake compared with the general population. Improving uptake in these populations requires contextually tailored interventions. We conducted a realist review to identify interventions effective at improving measles, mumps and rubella (MMR) and human papillomavirus (HPV) vaccine uptake among underserved communities. METHODS: We searched MEDLINE, EMBASE, CINAHL, Cochrane and ProQuest for English language publications from 2005 to 2022. Following title and abstract screening, full texts were assessed for relevance. Grey literature and reference lists were also examined. Data extraction and analysis were performed independently by two reviewers. Programme theories were generated from included articles and data extraction focusing on context-mechanism-outcome configurations. RESULTS: Of 1942 screened titles, 87 studies underwent full-text review of which 34 met inclusion criteria. 10 primary intervention categories were identified: parental and youth education; clinical outreach; data infrastructure/quality improvement; health provider training; school-based education; digital technology for patients; cash incentives; home visits; comic books; community leaders' education; and consent policy changes. Analysis highlighting contextual factors enabling or hindering each intervention category's success was conducted. CONCLUSIONS: Multicomponent strategies proved the most effective, with strongest evidence supporting home visits, parental and youth education, school-based programmes, data infrastructure and quality improvement and healthcare provider training. Moderate evidence supported reminders/recall strategies, comic books and consent policy changes, while digital technology for patients and cash incentives showed limited effectiveness. Importantly, there is no one-size-fits-all solution. Policymakers and practitioners should tailor and adapt interventions to the unique cultural, social and economic contexts of each group to ensure success. PROSPERO REGISTRATION NUMBER: CRD42021268068.