Abstract
BACKGROUND: Influenza vaccination confers broad benefits in the elderly and certain high-risk populations, but its effectiveness in patients with acute heart failure (HF) is uncertain. Rates of influenza vaccination are low in China due to poor awareness, cultural misunderstandings, and cost. AIMS: To determine the effectiveness of influenza vaccination in patients with acute HF admitted to hospitals in China. METHODS: The second Population Assessment of Influenza and Disease Activity (PANDA II) study is a two-arm, parallel-group, county-level hospital-based, cluster randomized controlled trial to determine the benefits and risks of full access to routine free influenza vaccination before hospital discharge, compared to routine limited use of influenza vaccination, on the primary endpoint of death or hospital readmission. Consecutive hospitalized patients at each site are enrolled to a target of 50 participants in each autumn-winter influenza outbreak period (October to March) over 3 consecutive years to reach the required sample size. Patients are centrally followed up at 1, 3, 6, and 12 months after hospital discharge (or death if earlier). Site numbers varied across year according to predicted influenza activity and logistical reasons. CONCLUSIONS: This study offers a unique chance to clarify uncertainties surrounding the effectiveness of influenza vaccination in patients with HF and to lay the groundwork for future prevention strategies. TRIAL REGISTRATION: This trial was registered with the acronym PANDA II (Population Assessment of Influenza and Disease Activity) at ChiCTR.org.cn (ChiCTR2100053264). Registered on 17 November 2021.