Continued presence and functionality of PF4-antibodies 4.5 years after VITT diagnosis

Vaccine-induced Immune Thrombotic Thrombocytopenia (VITT) is characterized by thrombocytopenia and thrombosis, mediated by platelet-activating platelet factor 4 (PF4) antibodies following adenoviral COVID-19 vaccination. While initially considered transient, recent VITT cases revealed prolonged anti-PF4 seropositivity (~0.3-3 years, and in one case ~4 years).

How long can functional PF4 antibodies persist after VITT, and what are the clinical implications for thrombosis risk and long-term management?

We describe a VITT patient who presented with thrombocytopenia and thrombosis following Ad26.COV2·S vaccination, with a follow-up of ~4.5 years post-vaccination, including serial testing at five different timepoints with evaluation of anti-PF4 levels and anti-PF4-induced functional platelet aggregation.

Platelet-activating anti-PF4 remained present from onset of VITT until follow-up 4.5 years later, with chronic thrombocytopenia but without recurrent thrombosis under anticoagulation therapy. These findings underline the importance of continued monitoring of VITT patients post-vaccination, including assessment of optimal anticoagulation duration and long-term thrombotic risk.