To assess the impact of influenza vaccination on the overall systemic inflammatory response in patients undergoing cardiac surgery and investigate functional and clinical outcomes in vaccinated patients postoperatively.

The investigators propose to perform a single center, double-blind, randomized, placebo-controlled crossover trial analyzing the beneficial effect of the influenza vaccine in patients undergoing cardiac surgery. This study assesses the impact of the influenza vaccination on the overall systemic inflammatory response and investigates the functional and clinical outcome in vaccinated patients after cardiac surgery. The study sample will consist of patients undergoing cardiac surgery at Health Sciences North randomized into 2 groups: 1) those who receive the vaccine or placebo preoperatively, or: 2) those who receive the vaccine or placebo 4-6 weeks postoperatively. Subjects in both groups will be compared using standard laboratory tools to assess the level of various pro- and anti-inflammatory cytokines (IL-6, IL-8,TNF-alpha, IL-10) as well as other cardiac and inflammatory markers (troponins, CRP), at different time intervals intra- and post-operatively. Other clinical outcomes will also be collected prospectively and compared between the 2 groups. These include hemodynamic parameters as well as major postoperative events. Further assessments will include the Frailty Index and Scale (in patients 65+) and length of stay after surgery

Inclusion Criteria:

• Subjects who the investigator believes can and will comply with the requirements of the protocol (i.e. return for follow-up visits, and able to converse with study personnel)
• Age 18 years or older
• Undergoing major cardiac surgery using cardiopulmonary bypass

Exclusion Criteria:

• Have not received influenza vaccination in the past or cannot be vaccinated due to previous severe reaction to influenza vaccine, egg, latex, or thimerosol allergies, or refusal of vaccination
• Participant has received a community available influenza vaccine within <6 months
• History of Guillain-Barré syndrome
• Immunosuppressive disorders or medications (including oral prednisone >10 mg daily, recent chemotherapy treatment)
• Emergency cases as determined by the investigator or physician