Vaccine-induced (immune) thrombotic thrombocytopenia (VITT): Diagnosis, guidelines, and reporting

Coronavirus disease 2019 (COVID-19) occurs as a result of infection by the severe acute respiratory syndrome coronavirus (SARS-CoV-2) virus. COVID-19 shows high morbidity and mortality rates, in part determined by various factors and the presence of other comorbidities. To reduce infection rates, help prevent COVID-19, and reduce COVID-19 related morbidity and mortality, a number of COVID-19 vaccines were fast tracked to development, clinical trials, and emergency use authorization. As with all vaccination events, there is potential for side effects after immunization. Most of the side effects are mild, and severe adverse side effects are rare. One such rare event, occurring in 1 in 50,000–100,000 vaccine doses, is a condition called thrombosis with thrombocytopenia syndrome by government reporting agencies, but otherwise called vaccine induced (immune) thrombotic thrombocytopenia (VITT) by scientific researchers. VITT has only been confirmed in people vaccinated using adenovirus-based vaccines. In this chapter, we review the diagnosis, guidelines, and reporting of VITT.