From the Guidelines
COVID-19 vaccines do not require prophylaxis with anticoagulants or antiplatelet agents for reducing the risk of adverse outcomes in nonhospitalized patients with thrombophilia, as stated in the 2023 ISTH update of the 2022 ISTH guidelines for antithrombotic treatment in COVID-19 1. The risk of thromboembolism associated with COVID-19 vaccines is a concern, but the current evidence suggests that the benefits of vaccination outweigh this risk.
- The 2023 ISTH guidelines recommend against prophylaxis with anticoagulants or antiplatelet agents for nonhospitalized patients with thrombophilia who receive a COVID-19 vaccine, citing a lack of benefit in reducing adverse outcomes 1.
- For patients with suspected vaccine-induced immune thrombotic thrombocytopenia (VITT), the guidelines recommend using antiplatelet factor 4 enzyme immunoassays for diagnosis, rather than rapid heparin-induced thrombocytopenia assays 1.
- Treatment of VITT may involve nonheparin anticoagulants, and when these are unavailable, treatment with unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH) is reasonable, according to the guidelines 1.
- Intravenous immune globulin (IVIG) may be considered for reducing the risk of death in patients with VITT, although the evidence for this is weak 1. It is essential to weigh the risks and benefits of COVID-19 vaccination, considering the individual's medical history and the specific vaccine being used.
- The mRNA vaccines (Pfizer-BioNTech and Moderna) are preferred options for individuals with a history of blood clots or clotting disorders, as they have not shown the same risk pattern as the adenovirus vector vaccines (J&J or AstraZeneca).
- Symptoms of concern after vaccination, such as severe headache, abdominal pain, leg pain, or shortness of breath, should prompt immediate medical attention.
From the Research
Covid Vaccine and Thromboembolic Risk
- The risk of thromboembolic events, such as deep vein thrombosis and pulmonary embolism, has been observed in patients with COVID-19 2, 3, 4.
- Studies have also investigated the risk of thromboembolic events after COVID-19 vaccination, with some reports suggesting a possible link between vaccination and thromboembolism 5, 6.
- A systematic review of vaccine-induced thrombotic thrombocytopenia found that young individuals, particularly females, may be more susceptible to this condition after receiving COVID-19 adenoviral-vector-based vaccines 5.
- Another study found that the incidence of deep vein thrombosis, pulmonary embolism, and bleeding was increased after COVID-19, with the highest risk ratios observed in patients with critical COVID-19 4.
- A case report described a possible link between the Pfizer-BioNTech BNT162b2 mRNA COVID-19 vaccine and thromboembolism, with a 59-year-old woman developing extensive deep vein thrombosis and pulmonary thromboembolism 7 days after receiving her first dose of the vaccine 6.
Thromboembolic Risk Factors
- The risk of thromboembolic events in COVID-19 patients is high, but varies greatly with the severity of the disease 2.
- Screening and absence of anticoagulation were associated with a higher incidence of venous thromboembolism in COVID-19 patients 2.
- The use of thromboprophylaxis in all COVID-19 inpatients is recommended, with clinical trials needed to test different thromboprophylaxis regimens in subgroups of COVID-19 inpatients 2.
- The incidence of thromboembolic complications and mortality associated with these complications can vary widely among hospitalized COVID-19 patients, highlighting the need for individualized thromboprophylaxis management plans 3.