The aim of this observational study is to determine if and how kidney failure affects the development of protective immune responses following vaccination in patients on chronic dialysis.

Researchers will compare the effectiveness of the influenza vaccine in inducing protective antibodies between hemodialysis patients and subjects without chronic kidney disease.

Participants will:

• Be enrolled at the time of influenza vaccination
• Visit the clinic at 7, 14, 30, 60, and 120 days after vaccination
• Be asked to provide relevant clinical information and a blood sample at each visit

Inclusion Criteria:

• Age between 18 and 70 years
• Patients undergoing thrice-weekly hemodialysis / peritoneal dialysis for at least 3 months OR healthy individuals without a history of renal insufficiency
• Subjects eligible to receive a seasonal influenza vaccine
• Signed informed consent for participation in the study

Exclusion Criteria:

• Recent influenza infection (clinically resolved less than 3 months ago).
• Administration of immunosuppressive drugs in the two weeks prior to vaccination.
• Administration of another vaccine in the three weeks prior to enrollment (co-administration of other vaccines with those under study does not contraindicate participation).
• Systemic infection clinically resolved less than two weeks before enrollment.

The study populations consist of (1) subjects with advanced chronic kidney disease requiring thrice-weekly hemodialysis, (2) subjects with advanced chronic kidney disease on peritoneal dialysis, and (3) subjects without a prior medical history of chronic kidney disease, who are eligible to receive an influenza vaccine according to standard clinical practice guidelines.