1 . Abstract 1.1 Background and Objectives Hemodialysis patients are prone to infection with SARS-COV2 and show a high probability of a severe course of disease and high mortality when infected . In many countries hemodialysis patients are prioritised in vaccination programs to protect this vulnerable community . However, no hemodialysis patients were included in efficacy trials of SARS CoV-2 vaccines and therefore efficacy and safety data for this patient group are lacking . These data would be critical, since hemodialysis patients showed decreased responses against various other vaccines and this could mean decreased response to SARS CoV-2 vaccines . 1.2 Design, setting, participants, and measurements We conducted a prospective cohort study consisting of a group of 81 hemodialysis patients and 80 healthy controls who were vaccinated with mRNA vaccine BNT162b2 (BionTech/Pfizer , 2 doses with an interval of 21 days). Anti-SARS-COV-2 S antibody response in all participants was measured 21 days after the second dose . The groups were compared with univariate quantile regressions and a multiple analysis . Adverse events (AEs) of the vaccination were assessed with a standardized questionnaire . We also performed a correlation of HBs-Antibody response with the SARS-COV-2 antibody response in the hemodialysis patients . 1.3 Results Dialysis patients had significantly lower Anti-SARS-COV-2 S antibody titres than healthy control patients 21 days after vaccination with BNT162b2 (median dialysis Patients 171 U/ml versus median controls 2500 U/ml). Age also had a significant but less pronounced influence on antibody titres . Dialysis patients showed less AEs than the control group . No significant correlation was found for Hepatitis B vaccine antibody response and SARS CoV-2 vaccine antibody response . 1.4 Conclusions Hemodialysis patients exhibit highly diminished SARS-COV-2 S antibody titres compared to a cohort of controls . Therefore these patients could be much less protected by SARS CoV-2 mRNA vaccination than expected . Alternative vaccination schemes must be considered and preventive measures must be maintained after vaccination.