Vaccination Against COVID-19 in Patients Treated With Anticoagulants
Canadian professional societies and the National Health Service (NHS) in the United Kingdom recommend COVID-19 vaccination even for patients treated with anticoagulants. The benefit of vaccination in these patients significantly outweighs the risk of hematoma associated with intramuscular injection. The recommendation applies to both warfarin and direct oral anticoagulants (DOACs).
Data in the SPC of Vaccines
Given the data in the SPC of COVID-19 vaccines, which state that the vaccine should either not be administered intramuscularly to patients on anticoagulant therapy, or should be administered with caution unless the benefits clearly outweigh the risks, doubts may arise as to whether these patients should be vaccinated. This question is particularly pressing as it mostly concerns older individuals at higher risk of severe COVID-19.
Opinion of Canadian Professional Societies
The Canadian professional society Thrombosis Canada addressed this issue in January 2021 and issued a statement emphasizing that anticoagulation therapy should not be a barrier to COVID-19 vaccination. The bleeding risk at the injection site after intramuscular administration of the vaccine and subsequent formation of a hematoma is significantly outweighed by the benefit of vaccination. Hence, COVID-19 vaccination is recommended for patients treated with warfarin, DOACs (dabigatran, edoxaban, apixaban, rivaroxaban), and antiplatelet drugs (aspirin, clopidogrel, ticagrelor). Although there is a small risk of hematoma formation at the injection site, serious consequences are not expected. Applying pressure at the injection site for 3–5 minutes post-vaccination can help prevent hematoma formation. Thrombosis Canada also states that additional INR determination is not necessary before vaccine administration for patients treated with warfarin. INR monitoring should continue according to the original schedule.
The National Advisory Committee on Immunization (NACI) of Canada supported Thrombosis Canada's stance and stated that “individuals on long-term anticoagulation therapy are not considered to be at increased risk of bleeding complications after vaccination and can be safely vaccinated without discontinuing anticoagulation therapy”.
Opinion of the British NHS
The NHS Foundation Trust advises that COVID-19 vaccines can be administered intramuscularly to individuals treated with DOACs or warfarin, provided that their most recent INR level within standard monitoring is below the upper therapeutic range. They recommend using a fine needle, applying at least 2 minutes of pressure at the injection site post-vaccination, and informing the patient about the possibility of hematoma formation.
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Sources:
1. Murdoch L.-A. Should COVID-19 vaccine be given to patients taking oral anticoagulants? CanadianHealthcareNetwork.ca, 2021 Jan 11. Available at: https://thrombosiscanada.ca/wp-uploads/uploads/2021/01/CHN-Physicians-Article-Anticoag-and-COVID-19-Vaccine.pdf
2. Bramley D. Using COVID-19 vaccines in patients with anticoagulation and bleeding disorders. Guy's and St Thomas' NHS Foundation Trust, 2021 Aug 8. Available at: www.sps.nhs.uk/articles/using-covid-19-vaccines-in-patients-with-anticoagulation-and-bleeding-disorders
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