Background Preventative health services, such as screening, vaccinations, and referrals to health and social services, improve health outcomes and reduce healthcare utilisation, costs, and inequities. People experiencing homelessness have significant unmet needs, but data are lacking on preventative health service provision. We aimed to review literature on hospital-based preventative health services for people experiencing homelessness.

Methods We systematically searched MEDLINE, Embase, PsycINFO, HMIC, CINAHL, Web of Science, and The Cochrane Library. We hand-searched the bibliographies and citing references of included studies. We included experimental and observational quantitative studies involving preventative health services in emergency departments or inpatient hospital settings from 1999–2019. The population included adults experiencing homelessness in high income countries. We included outcomes for health, social factors, healthcare utilisation, and healthcare costs. We managed studies in Endnote and extracted data using a standardised spreadsheet. We assessed quality and bias using the ‘Quality Assessment Tool for Quantitative Studies’ and narratively synthesised findings.

Results We identified 7935 articles from searches and reviewed 149 full text articles. Thirty-two met our eligibility criteria and were conducted in the USA (n=15), UK (n=9), Canada (n=4), and Australia (n=4). Sixteen studies were undertaken in emergency departments, 13 in inpatient wards, and 3 were conducted in both settings. We identified eight intervention categories: 1) homelessness screening, 2) case management, 3) screening, treatment initiation and referrals, 4) vaccinations, 5) discharge planning, 6) assistance with social needs, 7) pharmacological treatment, and 8) psychosocial services. Most studies described multi-component interventions. Results showed improvements in housing status, mental health, quality of life, and uptake of vaccinations and screening. Some studies reported successful integration with follow-up services, while others reported poor rates of onward care. Studies tended to report reductions in unplanned healthcare utilisation and costs, though not consistently. None showed harms. The overall strength of the evidence was weak to moderate with few randomised controlled trials.

Discussion Hospital-based preventative health services can improve housing status and health and may reduce unplanned healthcare utilisation and costs for people experiencing homelessness. Definitive data are lacking for effective integration across healthcare systems. Policy-makers and practitioners should consider providing hospital-based preventative services to tackle unmet needs and health inequities. Our study is limited by the lack of qualitative, grey literature, and non-English studies. Future research should investigate barriers and levers for successful implementation of hospital-based preventative health services and the integration of hospitals with primary care and other services.