Abstract Number: PB0341
Meeting: ISTH 2022 Congress
Background: Thrombotic thrombocytopenic purpura (TTP) has occasionally been described after vaccination. Since the availability of anti-SARS-CoV-2 vaccines, 12 cases have been described on a possible association with TTP onset.
Aims: This study aims to evaluate the relapse rates in patients affected by TTP undergoing anti-SARS-CoV-2 vaccination.
Methods: All consecutive TTP patients undergoing anti-SARS-CoV-2 vaccination from March to May 2021 were enrolled. Blood samples were collected before vaccination (T0), 2 weeks after the first (T1) and the second dose (T2) to evaluate ADAMTS13 activity and anti-ADAMTS13 antibody titer.
Results: A total of 49 TTP patients were enrolled (48 acquired and 1 congenital), all vaccinated with an mRNA vaccine.
No patients had a clinical TTP relapse, with an ADAMTS13 relapse rate of 1.36% per month. Mean levels of ADAMTS13 activity were stable among the three timepoints (Figure). In only two patients a significant drop in ADAMTS13 levels occurred after the first dose (from 28% to < 3% and from 101% to 82%), and both remained stable after the second dose, with negative anti-ADAMTS13 antibodies. Due to a stable undetectable ADAMTS13, the first patient was treated with 4 doses of weekly 375 mg/m2 rituximab with a rapid ADAMTS13 response. One patient had positive basal anti-ADAMTS13 antibodies with a titer remaining stable after the two vaccine doses, while in another patient anti-ADAMTS13 antibodies became detectable after the first dose, with no corresponding drop in ADAMTS13 levels and a stable titer after the second dose.
Conclusion(s): The result of our study prospectively evaluating the effect of anti-SARS-CoV-2 vaccination on the risk of relapse in a large cohort of patients with TTP in Milan showed a lower than reported relapse rate (1.36% vs 2.6%) with an observed to expected incidence rate ratio of 0.52, confirming the safety of mRNA-based anti-SARS-CoV-2 vaccination in TTP patients.
To cite this abstract in AMA style:Capecchi M, De Leo P, Biganzoli M, Mancini I, Agosti P, Ferrari B, Gualtierotti R, Artoni A, Peyvandi F. Impact of SARS-CoV-2 Vaccination in Thrombotic Thrombocytopenic Purpura Patients [abstract]. https://abstracts.isth.org/abstract/impact-of-sars-cov-2-vaccination-in-thrombotic-thrombocytopenic-purpura-patients/. Accessed September 29, 2023.
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