Thrombosis with thrombocytopenia syndrome (TTS), also known as vaccine-induced immune thrombotic thrombocytopenia (VITT), is recent, extremely rare but serious complication of adenovirus vector vaccines (e.g. ChAdOx1 nCoV-19 (Oxford-AstraZeneca) and AD26.COV2·S (Johnson & Johnson)). Discuss the two conditions, thrombosis and thrombocytopenia, with reference to TTS/VITT.