Hemostatic Markers, Adamts-13 Profile and Anti-Sars-Cov-2 Antibody Levels in Patients with Immune Thrombotic Thrombocytopenic Purpura Receiving BNT162b2 Vaccination

• Published in: Blood 2021-11, Vol.138 (Supplement 1), p.1022-1022
• Main Authors: Schieppati, Francesca, Russo, Laura, Marchetti, Marina, Galimberti, Elisa, Palladino, Angela Maria, Gamba, Sara, Verzeroli, Cristina, Tartari, Carmen Julia J, Bolognini, Silvia, Ticozzi, Chiara, Giaccherini, Cinzia, Barcella, Luca, Falanga, Anna
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2021-153606

▪ Introduction: Patients (pts) with immune thrombotic thrombocytopenic purpura (iTTP) are at high risk of severe COVID-19, therefore protection from SARS-CoV-2 by vaccination is particularly relevant in this setting, although concerns may exist on possible adverse reactions or disease relapse after vaccination. In this study, in a group of iTTP pts who received in-hospital COVID-19 vaccination in a special program for ‘fragile patients’, we prospectively evaluated over time the antibody response, the clinical and laboratory disease parameters and hemostatic biomarker levels. Methods: Twelve iTTP pts in clinical remission and regularly followed-up in our Center were enrolled in April 2021, all of them received 2 doses of BNT162b2 vaccine (Pfizer-BioNTech) over 21 days, and were followed-up for clinical and laboratory testing for 60 days. Blood samples were collected at enrollment (day 0, D0) before the 1 st vaccine dose; on day 21 (D21) before the 2 nd dose; and on day 60 (D60) after the 1 st dose. Blood cell counts, anti-Spike receptor-binding-domain protein (anti-S/RBD) IgG, ADAMTS-13 activity, and anti-ADAMTS-13 IgG (chromogenic assay and ELISA), were measured at each time point. Additionally, an extensive study of hemostatic markers (i.e. FVIII, von Willebrand Factor (vWF) antigen and activity, fibrinogen, D-dimer, tPA, PAI, and F1+2) was performed. Follow up is currently continuing. Results: Median age of our cohort was 65 years with M/F ratio of 4/8. Median time since last acute iTTP episode was 40 months, median follow up of the cohort was 71 months (95% CI 30-126). All pts were in clinical remission, except one patient (P1) who had an iTTP relapse after contracting SARS-CoV-2 infection, in Dec 2020, and was on low-dose steroids on D0. One patient (P2) had an ADAMTS-13 relapse in Jan 2021, and received pre-emptive rituximab. No other pts were on immunosuppressive therapy. Concerning the status of ADAMTS-13 activity on D0, 6 pts showed normal levels (>50%), while 5 had a moderate (50-20%) and 1 a complete (