Vaccine-induced Immune Thrombocytopenia and Thrombosis (VITT)

摘要

The coronavirus disease 2019 (COVID-19) pandemic has affected every part of the world, causing major morbidity and mortality as well as impacting heavily on the economy of every nation. As for other infectious diseases, vaccination is seen as the primary way to control the infection. A number of vaccines against COVID-19 have now been approved internationally. The AstraZeneca Oxford (AZ) COVID-19 vaccine was approved by the Medicines and Healthcare Products Regulatory Agency (MHRA), the UK regulator, on December 30, 2020, and by the European Medicines Agency (EMA), the European regulator, on January 29, 2021. This is one of the most widely used COVID-19 vaccines worldwide. Concerns about a high number of unusual thrombotic events following vaccination with the AZ vaccine started to grow in early March 2021. On March 11, 2021, both the MHRA and the EMA provided reassurance that the number of events observed was no higher than expected and advised the continued use of this vaccine as the benefits outweighed the risks.1,2 Within a week, however, researchers from Norway, Germany, and the United Kingdom reported on a group of patients who had been previously healthy but were admitted within 3 weeks of AZ vaccination with an unusual combination of cerebral venous sinus thrombosis (CVST) and thrombocytopenia. All three groups independently identified that their patients had circulating antibodies against platelet factor 4 (PF4), which were detected using the heparin-induced thrombocytopenia (HIT) ELISA assay.