This is a retrospective, multicenter, non-interventional cohort study based on data derived from existing electronic medical records. The study collects data on patient demographic and clinical characteristics, infection diagnosis, triage vital signs, laboratory values, and comorbidities in adults enrolled in the Emergency Department-initiated Hospital-at-Home (ED/HaH) model under Taiwan's National Health Insurance Administration (NHIA) Acute Care at Home (ACAH) Pilot Program.

For patient selection, enrollment in the NHIA ACAH Model C pathway was used as the index event. The patient selection period extends from August 1, 2024 to January 1, 2026. All adult patients (aged ≥18 years) with a primary diagnosis of pneumonia, urinary tract infection (UTI), or skin and soft tissue infection (SSTI) - confirmed by ICD-10 codes - who were enrolled directly from the emergency department at one of three participating tertiary medical centers (Chi-Mei Medical Center, Wan-Fang Hospital, and Taipei Medical University Hospital) during that period were considered for inclusion. Patients were identified through electronic medical record queries, and data were abstracted using a standardized case record form applied uniformly across all sites.

The primary outcome is HaH program failure, defined as any unanticipated care escalation (emergency department transfer, inpatient admission, or ICU admission within 48 hours of ED transfer) or death occurring during the HaH episode prior to planned completion. The program failure rate and characteristics of failure events - including failure type, clinical disposition, and time from HaH initiation to failure - will be described. As a secondary objective, exploratory multivariable analysis will examine whether demographic and clinical variables measured at ED enrollment show potential associations with program failure.

A total of 472 HaH episodes from 420 unique patients were analyzed. Statistical analyses will be performed for the overall cohort.

Inclusion Criteria:

• Enrolled under Model C of the National Health Insurance Administration (NHIA) Acute Care at Home (ACAH) Pilot Program at one of the three participating centers.
• Formally assessed and cleared for home care by the specialized interdisciplinary Hospital-at-Home (HaH) team using a standardized screening tool.
• Functional status meeting at least one of the following: a Barthel Index score of less than 60, or documented difficulty accessing outpatient care due to the nature of the illness, as assessed by the attending emergency physician.
• A primary diagnosis of pneumonia, urinary tract infection (UTI), or skin and soft tissue infection (SSTI), either alone or in combination, confirmed by ICD-10 codes.
• Clinical requirement for antimicrobial therapy, including intravenous antibiotic administration.
• Written informed consent obtained from the patient or their legal representative during the historical clinical encounter.

Exclusion Criteria:

• Hemodynamic instability, defined as persistent systolic blood pressure <90 mmHg despite initial fluid resuscitation, or any clinical requirement for intensive care unit (ICU) level monitoring or care.
• Immediate need for inpatient-only medical resources, including immediate surgical intervention, initiation of hemodialysis, or advanced diagnostic procedures not feasible in a home setting.
• Unsafe or unsuitable home environment, including absence of adequate caregiver support, hazardous living conditions, or severe cognitive or behavioral conditions that preclude adherence to the home treatment plan.

This study description focuses on patients who participated in Model C of the National Health Insurance Administration's Acute Care at Home Pilot Program across three participating medical centers between August 1, 2024, and January 1, 2026. The population comprises individuals initially presenting to the emergency department with any of the target primary acute infections-specifically pneumonia, urinary tract infection, or skin and soft tissue infection(either alone or in combination)- who were subsequently transitioned to the Hospital-at-Home care model.