At least 17 cases of thrombosis and thrombocytopenia have been reported in patients who received the Johnson & Johnson COVID-19 vaccine in the United States. Such events have been reported in patients who received the AstraZeneca vaccine as well. In this episode, Adam C. Cuker, MD, of the University of Pennsylvania, Philadelphia, tells host David H. Henry, MD, how to identify and manage patients with these vaccine-induced events. What’s in a name? The phenomenon of vaccine-induced thrombosis and thrombocytopenia has been given different names, including: Vaccine-induced immune thrombotic thrombocytopenia (VITT) Vaccine-induced prothrombotic immune thrombocytopenia (VIPIT) Thrombosis and thrombocytopenia syndrome (TTS). Dr. Cuker’s preferred acronym is VITT. VITT is an immune-mediated reaction to the Johnson & Johnson and AstraZeneca vaccines that “results in thrombocytopenia and a strong propensity for thrombosis,” Dr. Cuker explained. Dr. Henry noted that VITT is reminiscent of heparin-induced thrombocytopenia (HIT). Incidence unclear VITT appears to be “very rare,” but “we still don't have a great sense of how common it is” because additional cases may not have been recognized or have yet to present, Dr. Cuker said. VITT occurs about 5-30 days after vaccination. VITT appears to be mediated by IgG antibodies, which take time to build up. The exact mechanism is unknown, but VITT could be related to the adenovirus vector used in the Johnson & Johnson and AstraZeneca vaccines, Dr. Cuker said. The first 15 cases of VITT associated with the Johnson & Johnson vaccine occurred in women, and most patients were aged under 50 years. In Canada, where the AstraZeneca vaccine is available, cases of VITT have been reported in patients in their 80s and 90s. Diagnosing VITT Symptoms of VITT can include severe, unrelenting headache; severe abdominal pain; nausea and vomiting; as well as typical signs and symptoms of deep vein thrombosis or pulmonary embolism. To determine if a patient has VITT, Dr. Cuker recommends ordering a disseminated intravascular coagulation panel – prothrombin time, partial thromboplastin time, fibrinogen, and D-dimer – as well as a standard HIT enzyme-linked immunosorbent assay (ELISA). Rapid immunoassays for HIT are not reliable for VITT, so HIT ELISA must be used, Dr. Cuker emphasized. Most patients with VITT have a “strongly positive” ELISA with optical density values “well in excess of 100 or 1.0,” depending on the scale, Dr. Cuker said. Manage VITT like HIT Patients should receive an anticoagulant, but not heparin, Dr. Cuker said. It isn’t clear if heparin will be harmful in patients with VITT, but current guidelines recommend avoiding heparin. He also advised against using warfarin or vitamin K antagonists in patients with VITT “at least until their platelet count recovers.” High-dose intravenous immunoglobulin (e.g., 1 g/kg for 2 consecutive days) is recommended, as it is believed to interfere with platelet activation. Show notes written by M. Alexander Otto, a reporter for MDedge and Medscape. Disclosures Dr. Henry has no relevant disclosures. Dr. Cuker has served as a consultant for Synergy Pharmaceuticals; has received authorship royalties from UpToDate; and his institution has received research support on his behalf from Alexion, Bayer, Novartis, Novo Nordisk, Pfizer, Sanofi, Spark Therapeutics, and Takeda. *  *  * For more MDedge Podcasts, go to mdedge.com/podcasts Email the show: podcasts@mdedge.com Interact with us on Twitter: @MDedgehemonc David Henry on Twitter: @davidhenrymd