- hiv seropositivity - pregnancy - active malignant disease at inclusion - current grade iii-iv acute graft versus host disease (gvhd) - in vitro t-cell depletion of the graft if vaccination within the 6 months after transplantation. - rituximab administration in the 6 months prior to study inclusion - prior documented covid-19 infection

- hiv seropositivity - pregnancy - active malignant disease at inclusion - current grade iii-iv acute graft versus host disease (gvhd) - in vitro t-cell depletion of the graft if vaccination within the 6 months after transplantation. - rituximab administration in the 6 months prior to study inclusion - prior documented covid-19 infection