AMBU-VAX is a prospective, single-center observational study designed to develop and implement an organizational model for delivering recommended vaccinations within a hospital setting.

The study targets adult and elderly patients with chronic diseases or immunocompromising conditions who are eligible for vaccination according to national immunization guidelines. Vaccination is actively proposed during outpatient visits, hospital admissions, or at discharge and, when accepted, administered within the hospital or coordinated with local public health vaccination services.

The study aims to evaluate the feasibility, uptake, and completion of hospital-based vaccination pathways and to support integration between hospital and territorial prevention services for vulnerable populations.

Vaccination coverage among hospitalized and chronically ill patients remains suboptimal despite strong national and international recommendations. Hospital settings represent a strategic opportunity to identify vulnerable patients, reduce missed vaccination opportunities, and improve access to preventive services.

AMBU-VAX is a prospective observational study conducted at Fondazione Policlinico Universitario "A. Gemelli" IRCCS, Rome. The study targets adult patients affected by chronic diseases or immunocompromising conditions eligible for recommended vaccinations according to the Italian National Immunization Plan 2023-2025.

Patients are identified during outpatient visits, hospital admissions, or at discharge. Vaccination is actively proposed and, when accepted, administered within the hospital vaccination clinic or ward. When appropriate, patients are referred to local vaccination services to complete their immunization schedule.

Primary outcomes include vaccination offer, vaccine uptake, number of administered doses, and completion of vaccination pathways within the hospital setting. Secondary outcomes include reasons for vaccine refusal and referral to territorial vaccination services.

The study aims to assess the feasibility, effectiveness, and sustainability of a hospital-based vaccination model that can be replicated in other healthcare settings.

Inclusion Criteria:

• Adults aged ≥18 years
• Presence of at least one chronic or immunocompromising condition eligible for vaccination according to national guidelines
• Written informed consent provided

Exclusion Criteria:

• Age <18 years
• Conditions not included among the predefined eligibility criteria

The study population includes adult patients (≥18 years) with chronic diseases or immunocompromising conditions who are eligible for recommended vaccinations according to the Italian National Immunization Plan 2023-2025.

Patients are identified during outpatient visits, hospital admissions, or at discharge from the Fondazione Policlinico Universitario "A. Gemelli" IRCCS. The population includes both male and female patients and reflects a broad spectrum of chronic and immunocompromising conditions, including cancer, solid organ transplantation, hematopoietic stem cell transplantation, autoimmune diseases, chronic kidney disease, HIV infection, asplenia, and frailty.