Vaccination strategies for high-risk and fragile populations in Lombardy (Italy): a region-wide assessment of hospital-based models and best practices.

Background: Subjects with selected underlying medical conditions are at higher risk of infection and severe outcomes from vaccines preventable diseases. While most countries adopt life-course approaches to vaccination, high-risk group immunization programmes could maximize individual protection, while contributing to population health. The COVID-19 pandemic stimulated the planning and implementation of successful hospital-based high-risk groups' immunization models. However, in Italy, high-risk subjects' vaccine coverage is not actively monitored at the national or regional level, nor shared guidelines exist yet on hospital-based immunization programmes.

Study design: The study reports findings from a region-wide assessment of the availability, characteristics, and setting-specific features of hospital-based immunization programmes for high-risk subjects in the Lombardy region.

Methods: Fondazione The Bridge a not-for-profit organization based in Milan, in collaboration with the Prevention Unit of the Lombardy Region Directorate for Welfare, and the University of Pavia coordinated a project aimed at bringing together regional health institutions, key stakeholders, academic experts, scientific societies and patients' associations to assess high-risk subjects' barriers to vaccine uptake and inform preventive programmes and policies. In this context, we designed and implemented a survey to systematically map the existence and characteristics of hospital-based immunization programmes targeting high-risk subjects. The survey was proposed to all 115 hospital medical directions of the Lombardy region.

Results: We collected data from 97 hospital medical directions, with a response rate of 85%. Among respondents, 24% were publi-cly managed hospitals, 17% were Scientific Institute for Research, Hospitalization and Healthcare (IRCCS) and 59% accredited private hospitals. Overall, 51.5% facilities in the Lombardy Region reported to actively administer vaccines to high-risk subjects in hospital settings, the prevalence being 89.6% in public hospitals. Among hospitals where vaccines are actively administered, 46% reported to have centralized vaccines ambulatory clinics, while 54% reported to administer vaccines in the context of inpa-tient care, within clinical wards. In 14% of hospitals vaccination counselling is carried out at the hospital level, while patients are referred to community services for the vaccine administration, 58% have established clinical pathways and formalized internal procedures to integrate vaccine prevention within the clinical care.

Conclusions: Half of hospital facilities in the Lombardy Region administer vaccines to high-risk patients. Hospital-based im-munization models vary widely by vaccines programmes, organizational aspects, vaccines procurement and workforce involved. Identifying best practices and effective models can help tackle current challenges and improve immunization coverage for at-risk groups.