摘要：
Background Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection results in poor outcome in patients with hematologic malignancies. Moreover, the efficacy of anti-SARS-CoV-2 mRNA vaccines appears lower in immunocompromised patients, including recipients of allogeneic stem cell transplantation (Allo-HSCT). In this population, data are scarce regarding factors predicting the response to mRNA vaccines. Methods This retrospective study aimed to decipher which factors, including immune status at time of vaccine and recipient/donor blood groups, might influence the antibody response after two injections (V1 and V2) of BNT162b2 (Pfizer-BioNTech) vaccine in a cohort of allografted patients with no previous symptomatic nor asymptomatic COVID-19 infection. Possible previous asymptomatic COVID-19 infection was investigated in pre-V1 samples by testing for anti-nucleocapsid (N) antibodies (anti-SARS-CoV-2 immunoassay, Roche Elecsys®, Rotkreuz, Switzerland). Antibody response to the SARS-CoV-2 spike protein receptor-binding domain was tested post-V2 (Roche Elecsys®). As recommended by the manufacturer, titers ≥0.8 U/mL were considered positive, the highest value being >250 U/mL. Blood samples were also collected before V1 and at distance from V2 to evaluate, by flow cytometry, total lymphocyte (Ly) counts and quantitative Ly subsets (CD3, CD4 and CD8 T cells, B and NK cells). Statistical analyses were performed on R (version 4.0.3). Patient characteristics were compared by using the Χ² test for discrete variables and the Wilcoxon test for continuous variables. Generalized linear models were used to conduct multivariate analyses. Results Samples were available from 117 Allo-HSCT patients who had been vaccinated between January 20 and April 17, 2021. Patient characteristics are provided in Table 1. The average interval from Allo-HSCT day 0 (D0) to V1 (D0-V1) was 654 (IQR: 372-1367) days (d). S-antibody response rate post-V2 was 82.9% for the entire cohort. Non-hum
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