This guideline covers vaccine-induced immune thrombocytopenia and thrombosis (VITT), a syndrome which has been reported in rare cases after COVID-19 vaccination. VITT may also be called vaccine-induced prothrombotic immune thrombocytopenia (VIPIT) or thrombotic thrombocytopenic syndrome (TTS). Because VITT is a new condition, there is limited evidence available to inform clinical management, identification and management of the condition is evolving quickly as the case definition becomes clearer. This guideline was produced to support clinicians to diagnose and manage this newly recognised syndrome. NICE is continually monitoring the evidence. Future versions of the guideline will reflect changes in the evidence base and clinical practice. On 22 June 2022, we updated the advice on plasma exchange with fresh frozen plasma in people at high risk of a poor prognosis to recommend it is considered earlier in the care pathway. We have published this guideline in MAGICapp, a global evidence ecosystem already being used by key partners such as the Australian Taskforce for COVID-19 and the World Health Organization. The MAGICapp platform allows the efficient sharing of evidence between guideline developers from around the world. This means NICE can develop and update its COVID-19 guidance more quickly and efficiently as new evidence is assessed.