Thrombosis with thrombocytopenia syndrome
Thrombosis with thrombocytopenia syndrome (TTS) is a rare syndrome that involves acute venous or arterial thrombosis and new onset thrombocytopenia in patients with no recent known exposure to heparin. In the United States, the majority of people with TTS that occurred after Janssen COVID-19 vaccination had clots located in cerebral venous sinuses; clots also occurred in other unusual locations including in the portal vein and splenic vein, and included a combination of venous and arterial thromboses. FDA updated the Janssen COVID-19 vaccine EUA Fact Sheet for Health Care Providers Administering Vaccine (Vaccination Providers) and Fact Sheet for Recipients and Caregivers to include information about rare clotting events that might occur after vaccination, primarily among women aged 18–49 years.
Women aged <50 years
Women aged <50 years can receive any FDA-authorized COVID-19 vaccine. However, they should be made aware of the rare risk of TTS after receipt of the Janssen COVID-19 vaccine and the availability of other FDA-authorized COVID-19 vaccines (i.e., mRNA vaccines). The highest rates of TTS per vaccine doses administered were identified in women <50 years of age. At the time of ACIP’s review, TTS reporting rates to VAERS were 7.0 cases per million Janssen COVID-19 vaccine doses administered to women aged 18−49 years and 0.9 per million to women aged ≥50 years.
People with a history of thrombosis or risk factors for thrombosis
Although the etiology of TTS associated with the Janssen COVID-19 vaccine is unclear, it appears to be similar to another rare immune-mediated syndrome, heparin-induced thrombocytopenia (HIT). Until more information becomes available, experts advise that people with a history of an episode of an immune-mediated syndrome characterized by thrombosis and thrombocytopenia, such as HIT, should be offered another FDA-authorized COVID-19 vaccine (i.e., mRNA vaccine) if it has been ≤90 days since their TTS resolved. After 90 days, patients may be vaccinated with any FDA-authorized COVID-19 vaccine.
Venous thromboembolism (VTE), defined as deep vein thrombosis, pulmonary embolism, or both, are common. The biologic mechanisms for VTE (as well as arterial thrombi) differ from the underlying immune-mediated mechanism for HIT. Based on current knowledge, experts believe that people with risk factors for VTE (e.g., inherited or acquired thrombophilia including Factor V Leiden; prothrombin gene 20210A mutation; antiphospholipid syndrome; protein C, protein S or antithrombin deficiency), or a prior history of other types of thromboses (including cerebral venous sinus thrombosis [CVST]) not associated with thrombocytopenia are unlikely to be at increased risk for TTS. Likewise, although the risk of thrombosis is increased during pregnancy and the postpartum period, and with certain hormonal contraceptives (e.g., combined oral contraceptives, patch, and ring), experts believe that these factors do not make people more susceptible to TTS after receipt of the Janssen COVID-19 vaccine. People with risk factors for VTE can receive any FDA-authorized vaccine, including the Janssen COVID-19 vaccine.
Use of aspirin or anticoagulants
It is not recommended that people take aspirin or an anticoagulant before vaccination with the Janssen COVID-19 vaccine or any other FDA-authorized COVID-19 vaccine (i.e., mRNA vaccine) unless they take these medications as part of their routine medications.
People with a history of Guillain-Barré syndrome
Reports of adverse events following use of the Janssen COVID-19 Vaccine under EUA suggest an increased risk of GBS during the 42 days following vaccination. Investigations to assess whether there is a causal relationship between GBS and Janssen vaccine are ongoing. People with a history of GBS can receive any FDA-authorized COVID-19 vaccine. However, given the possible association between the Janssen COVID-19 vaccine and an increased risk of GBS, a patient with a history of GBS and their clinical team should discuss the availability of mRNA COVID-19 vaccines to offer protection against COVID-19.