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This article was originally published in Portuguese on Medscape.
Earlier this year, the Brazilian Society of Cardiology (SBC) released a position statement regarding evidence gathered on the cardiovascular safety of vaccines against COVID-19. Two cardiovascular adverse events were considered: vaccine-induced immune thrombotic thrombocytopenia (VITT), and myocarditis. The first part of the document, entitled "Position Statement on Cardiovascular Safety of Vaccines Against COVID-19 – 2022," highlights specific considerations and recommendations on COVID-19 vaccination for individuals with a previous history of venous thromboembolism (VTE) or who have a predisposition to VTE. The second part of the document considers those at risk of myocarditis.
The two rare adverse effects were identified during phase 4, or postmarketing, surveillance. This stage is crucial for evaluating the occurrence of rare adverse events for which causal relationships with vaccines can only be established after the vaccines have been administered to a large number of people.
In February 2021, VITT, a postthrombotic syndrome, was described in some vaccinated individuals. Two adenovirus-vectored vaccines have been implicated in the cause of VITT: ChAdOx1S nCoV-19 (Oxford/AstraZeneca and Serum Institute of India) and Ad26.COV2.S (Janssen; Johnson & Johnson). It should be noted that the real incidence of VITT is still unknown, and evidence has suggested that it is a rare complication.
