Following reports of thrombotic events in atypical sites (thrombosis of the cerebral venous sinuses and/or of the splanchnic district), associated with thrombocytopenia and with particularly serious clinical courses, in subjects vaccinated against SARS-CoV-2 with the viral vector vaccines Vaxzevria (ChAdOx1 nCov-19 from Astra Zeneca) and Janssen (Ad.26 COV2.S by Johnson & Johnson), AIFA has appointed a group of experts in coagulation pathologies (Haemostasis and Thrombosis Working Group) to support the Technical Scientific Committee (CTS). The mandate of the group was to investigate the biological plausibility of the events, identify possible risk minimisation strategies, and indicate the most appropriate methods for the clinical management of these very rare events.

The document (structured in questions and answers) represents the conclusions of the expert group and is intended to provide non-specialist physicians and healthcare professionals with the information currently available to identify early and manage this very rare adverse event in the most appropriate way.

For a detailed contextualisation of the risk of these complications, please refer to the conclusions of the EMA evaluation (https://www.aifa.gov.it/documents/20142/1289823/2021.04.23_com-EMA_COVID-19_AstraZeneca_IT.pdf and https://www.ema.europa.eu/en/documents/chmp-annex/annex-vaxzevria-art53-visual-risk-contextualisation_en.pdf).