Inclusion Criteria:  Chronic prevalent hemodialysis patients (for more than 3 months) performing 2 to 3 sessions / week, at least 3 hours, at the André Grégoire hospital center, Montreuil. Age> 18 years old, Vaccination of at least one dose of Pfizer or Moderna vaccine from January 1, 2021, performed during a dialysis session. Affiliation to a social security scheme;  Exclusion Criteria:  Acute hemodialysis (duration <3 months). Patient who died before the first vaccine dose. Age <18 years old Inability to give consent (eg mental retardation, patient under guardianship or legal protection, decompensated psychiatric illness, too advanced dementia (MMS <15/30, etc.) Pregnant women Patient participating in another interventional study