Strategies to improve vaccination rates in people who are homeless: A systematic review.

People who are homeless experience higher rates of vaccine-preventable disease, including COVID-19, than the general population, and poorer associated health outcomes. However, delivering vaccinations to people who are homeless is complex, and there is a lack of evidence to inform practice in this area. The aim of this systematic review is to: (a) identify, (b) analyse the characteristics of, and (c) evaluate the outcomes of, strategies to improve vaccination rates in people who are homeless. Literature was retrieved from eight electronic databases. Studies undertaken in high-income countries, published in English, in a peer-reviewed journal, and in full-text were considered. No limits were placed on study design or date. A total of 1,508 articles were retrieved and, after the removal of duplicates, 637 were screened. Twenty-three articles, reporting on nineteen separate vaccination strategies for hepatitis A/B, influenza, herpes zoster, invasive pneumococcal disease, and diphtheria in people who are homeless, were selected for inclusion. All the strategies were effective at improving vaccination rates in, people who are homeless. Most strategies involved vaccination clinics and most were delivered, at least in part, by nurses. Other characteristics of successful strategies included: delivering vaccinations at convenient locations; using accelerated vaccination schedules (if available); vaccinating at the first appointment, regardless of whether a person's vaccination history or serological status were known (if clinically safe); operating for a longer duration; offering training to staff about working with people who are homeless; widely promoting clinics; considering education, reminders, incentives, and co-interventions; ensuring no out-of-pocket costs; and working collaboratively with stakeholders, including people who are homeless themselves. These findings will inform evidence-based vaccination strategies, including for COVID-19, in people who are homeless, and improve associated health outcomes in this at-risk, hard-to-reach group.