Timing of Influenza Vaccination in Patients With Heart Failure

Heart failure (HF) is one of the most common causes of hospital admission in Canada and costs the Canadian healthcare system over $1 billion annually. Influenza vaccination is an inexpensive strategy to prevent influenza infections and reduce an important trigger for HF decompensation and hospital readmission. Yet, the optimal timing of vaccine administration remains unclear. When patients with HF are admitted to the hospital with an acute decompensation in advance of, or during, the 'flu season', this can be an ideal time to administer the vaccine. However, patients with acute HF decompensation have significant inflammatory injury, and may have substantially impaired immune responses; thus vaccine administration while admitted during an acute decompensated HF episode may not lead to high anti-influenza antibody titres. A more effective strategy can be to vaccinate after the decompensation has resolved, when patients are more stable. The FLU-HF randomized trial will determine whether administering the influenza vaccine to patients admitted in-hospital with an acute HF decompensation or waiting until they have stabilized as an out-patient leads to an improved anti-influenza response.