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VITT vs TTS Definitions

The distinction between VITT (vaccine-induced immune thrombotic thrombocytopenia) and TTS (thrombosis with thrombocytopenia syndrome) in the context of COVID-19 vaccines, including the impact of different definitions and laboratory tests on incidence estimates.

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Jan 11, 2026
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How do the clinical definitions of TTS, VITT and anti‑PF4‑positive cases differ and how does that affect incidence estimates?

VITT is a specific, pathogenic subset of the broader surveillance label TTS defined by clinical timing and laboratory proof of platelet‑activating anti‑PF4 antibodies, while “anti‑PF4‑positive” cases ...

Jan 12, 2026
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What genetic or immune risk factors have been identified that predispose people to VITT after adenovirus‑vector COVID‑19 vaccines?

Vaccine‑induced immune thrombotic thrombocytopenia (VITT) is driven by platelet‑activating antibodies against platelet factor 4 (PF4), and those antibodies are the central immune correlate that distin...