Most anti-PF4 antibodies in vaccine-induced immune thrombotic thrombocytopenia are transient

• Published in: Blood 2022-03, Vol.139 (12), p.1903-1907
• Main Authors: Schönborn, Linda, Thiele, Thomas, Kaderali, Lars, Günther, Albrecht, Hoffmann, Till, Seck, Sabrina Edigna, Selleng, Kathleen, Greinacher, Andreas
• Format: Article
• Language: English
• Subjects: ChAdOx1 nCoV-19; COVID-19 - prevention & control; COVID-19 Vaccines - adverse effects; Female; Heparin - adverse effects; Humans; Immunoglobulin G; Platelet Factor 4; Thrombocytopenia - chemically induced; Thrombosis; Thrombosis and Hemostasis; Vaccines - adverse effects
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood.2021014214

Vaccine-induced thrombotic thrombocytopenia (VITT) is triggered by vaccination against COVID-19 with adenovirus vector vaccines (ChAdOx1 nCoV-19; Ad26.COV2-S). In this observational study, we followed VITT patients for changes in their reactivity of platelet-activating antiplatelet factor 4 (PF4) immunoglobulin G (IgG) antibodies by an anti-PF4/heparin IgG enzyme immunoassay (EIA) and a functional test for PF4-dependent, platelet-activating antibodies, and new thrombotic complications. Sixty-five VITT patients (41 females; median, 51 years; range, 18-80 years) were followed for a median of 25 weeks (range, 3-36 weeks). In 48/65 patients (73.8%; CI, 62.0% to 83.0%) the functional assay became negative. The median time to negative functional test result was 15.5 weeks (range, 5-28 weeks). In parallel, EIA optical density (OD) values decreased from median 3.12 to 1.52 (P < .0001), but seroreversion to a negative result was seen in only 14 (21.5%) patients. Five (7.5%) patients showed persistent platelet-activating antibodies and high EIA ODs for >11 weeks. None of the 29 VITT patients who received a second vaccination dose with an mRNA COVID-19 vaccine developed new thromboses or relevant increase in anti-PF4/heparin IgG EIA OD, regardless of whether PF4-dependent platelet-activating antibodies were still present. PF4-dependent platelet-activating antibodies are transient in most patients with VITT. VITT patients can safely receive a second COVID-19 mRNA-vaccine shot. •Platelet-activating anti-PF4 antibodies in VITT are transient in >90% of patients.•Likely VITT patients can safely receive a second vaccination shot with an mRNA vaccine, independent of their VITT-antibody status. [Display omitted]