This study initiated a retrospective anal. of post-vaccination antibody levels and blood counts in patients with AA or AA/PNH overlap syndrome.Sixteen patients (8 female/8 male, median age 57.5 years, range 24- 69 years) were identified with sufficient data within the Aachen Registry for Telomeropathies and Aplastic Syndromes.All patients are currently undergoing immunosuppressive treatment including ATG and CSA and/or addnl. treatments with Eltrombopag or C5- complement inhibitors at the University Hospital of RWTH Aachen. All patients treated with ATG received horse ATG (ATGAM).Eighty-eight percent (14/16) of the patients received BTN162B2 (Pfizer/BioNTech), 6% (1/16) mRNA-1273 (Moderna), and 6% (1/16) ChAdOx1 (AstraZeneca), resp.Concerning asymptomatic SARS-CoV-2 infections, the patients did not report pos. results for SARS-CoV-2-specific PCR or rapid antigen test during follow-up.Anal. of the vaccination- induced antibody levels against the SARS-CoV-2 spike protein showed that all patients developed detectable antibody titers with a median of 553 BAU/mL (range 168- 1040 BAU/mL) within the first 6 mo after the second vaccination.Here, they found a continuous decline in antibody levels from a median of 848 BAU/mL (range 176- 1040 BAU/mL) after the 1st month to 410 BAU/mL (range 168- 1040 BAU/mL) in the 2nd month and to 367 BAU/mL (range 223- 936 BAU/mL) after 3 to 6 mo after the second vaccination.Our observation of declining antibody levels was further confirmed in six patients where individual follow- up measurements of the vaccination levels were available.The resp. episodes lasted approx. 6 wk after the first vaccination and 24 wk after the second vaccination with a min. of 0.96 neutrophilic granulocytes/nl.The anal. suggests that patients with AA and AA/PNH overlap syndrome under IST including C5 inhibitors can develop sufficient levels of spike protein- directed antibodies similar to levels observed in healthy individuals.Of note, even patients who were vaccinated within the first month after ATG administration showed at least modest immune response despite the known immunosuppressive effect of ATG on the T- and B- cell response.This observation suggests that SARS- CoV- 2 vaccinations can be at least partially effective and therefore argues in favor of vaccination closely after ATG administration.This study provide first data that patients with AA and AA/PNH overlap syndrome show similar antibody dynamics as observed in healthy individuals without evidence of relapse or relevant changes in blood counts.