Background: The preventive containment measures implemented in the COVID-19 pandemic are not feasible in chronic hemodialysis patients (HD) who need to attend their dialysis sessions 3 times a week. HD patients display frequent comorbidities (such as diabetes and cardiovascular disease), and immune deficiency, which expose them to an increased risk of severe forms of COVID-19. They can be infected in their dialysis center despite the measures taken to limit this risk. Their caregivers are also at risk of infection if patients carry the virus. Dialysis centers face major organizational challenges in terms of patient and caregiver safety. Knowing the viral serological status of HD patients and caregivers, the proportion of asymptomatic forms, and the persistence and effectiveness of immunization over time would be of major interest for patient management and the organization of dialysis care. Research objectives: The primary objective of SeroCOVIDial is to assess the prevalence of SARS-COV2 seroconversion at inclusion (M0) in a cohort of HD patients, using the rapid serological test. Secondary Objectives : 1) assess the prevalence of SARS-COV2 seroconversion in dialysis caregivers at M0, using the same test; 2) assess the proportion of asymptomatic forms of COVID-19 in HD patients and in their caregivers; 3) compare the prevalence of seroconversion and the proportion of asymptomatic forms in HD patients according to their clinical characteristics and co-morbidities; 4) assess the prevalence of SARS-COV2 seroconversion in participants who had a documented COVID-19; 5) evaluate the spread of the epidemic and the kinetics of seroconversion in patients and caregivers by a second test performed at M3; 6) evaluate the predictive value of SARS-COV2 seroconversion at M0 on the risk of developing a symptomatic COVID-19 infection within 6 months, in patients and caregivers; 7) evaluate a posteriori the intrinsic diagnostic performances of the test in comparison with serological gold standards (ELISA and seroneutralization). Methods: Multicenter cohort study, carried out in 4 dialysis facilities in Aix-Marseille. Procedure: collection of clinical data and rapid serological tests carried out at M0 and M3, in patients and caregivers (a systematic screening for COVID-19 symptoms has been carried out in all HD patients in the 4 participating centers since the beginning of the pandemic in France). Number of participants: 800 eligible persons (561 HD patients, and 239 caregivers). Material tested: rapid Biosynex serological test on 1 drop of blood, and 1 tube of frozen serum for patients at M0 and M3. Clinical data will also be collected. Primary endpoint: prevalence of SARS-COV2 seroconversion in HD patients. Maximum duration of participation for each patient: 6 months. Duration of research: 6 months and 2 weeks (inclusions over 2 weeks).