Subsequent vaccinations in VITT patients other than SARS-CoV2 vaccination

ABSTRACT

Introduction Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a rare, but severe side effect after vaccination with adenovirus vector-based vaccines (ChAdOx1 nCoV-19, AstraZeneca and Ad26.COV2.S, Johnson & Johnson/ Janssen) in which platelet activating anti-platelet factor 4 (PF4) antibodies cause thrombocytopenia and thrombosis at unusual sites. Patients and treating physicians are concerned about whether other vaccinations can also trigger thrombosis in patients with a history of VITT. We showed that VITT patients can safely receive their second and third vaccination against Covid-19 with an mRNA-based vaccine. [1] However, there is limited information on whether other vaccines than against Covid-19 could booster platelet activating anti-PF4 antibodies. Uncertainty increased after a report of VITT caused by human papilloma vaccination. [2] Method In our follow-up study of patients with laboratory confirmed VITT (EUPAS45098), an anti-PF4/heparin IgG enzyme immune assay (EIA) and a PF4-dependent platelet activation assay (PIPA) were performed at regular intervals and after each vaccination reported to us. Results Seventy-one VITT patients (43 female, median age at VITT diagnosis 48, range 18-80) were followed for a median of 56 weeks (range 13-77 weeks). During the follow-up period, eight vaccinations other than against Covid-19 were reported Six vaccinations against influenza (three Influvac, two Vaxigrip Tetra, one Influsplit Tetra) and two consecutive vaccinations against tick-borne encephalitis (TBE) in one patient. In six patients who received vaccination against influenza, all patients showed decreasing or stable EIA optical density (OD) levels. None of them showed a reactivation of platelet-activating anti- PF4-antibodies in the PIPA. The patient who was vaccinated against TBE twice showed stable EIA OD levels and remained negative in the PIPA throughout. No new thrombosis or recurrent thrombocytopenia were observed after any vac- cination. Five out of six patients still received therapeutic anticoagulation, one patient did not receive any anticoagulative drug (Fig. 1). Conclusion Similar to observations after consecutive mRNA-vaccinations against Covid-19 in VITT patients, vaccinations against influenza and TBE very unlikely reactivate platelet-activating anti-PF4-antibodies. Further follow up of the VITT patient cohort is performed to detect any new safety signal related to recurrence of VITT. (Table Presented).