SARS‐CoV ‐2‐reactive antibody detection after SARS‐CoV ‐2 vaccination in hematopoietic stem cell transplant recipients: Prospective survey from the Spanish Hematopoietic Stem Cell Transplantation and Cell Therapy Group

This is a multicenter prospective observational study which included a large cohort (n = 397) of allogeneic (allo-HSCT) (n = 311) and autologous (ASCT) hematopoietic stem cell transplant (n = 86) recipients who were monitored for antibody detection within 3 to 6 weeks after complete SARS-CoV-2 vaccination from February 1st 2021 to July 20th 2021. Most patients (n = 387, 97.4%) received mRNA-based vaccines. Most of recipients (93%) were vaccinated more than 1 year after transplant. Detectable SARS-CoV-2-reactive antibodies were observed in 242 (78%) of allo-HSCT and in 73 (85%) of ASCT recipients. Multivariate analysis in allo-HSCT recipients identified lymphopenia <1x109 /mL [Odds ratio (OR…