COVID Shot While on a Blood Thinner?
As COVID-19 vaccination continues to roll out to older and medically eligible people across the country, many questions arise for those taking blood thinners.
The most important point is that COVID-19 vaccine is fine for pretty much all individuals, no matter whether they have a thrombophilia, a prior deep vein thrombosis (DVT) or pulmonary embolism (PE), or are on a blood thinner.
Reasons not to get the vaccine have to do with allergies but not with the fact that a patient has had a clot or is on an anticoagulant. While COVID-19 infection is associated with an increased risk of DVT and PE, particularly in the very sick and hospitalized patient, there is no reason to believe that the vaccine would increase the risk for blood clots. Recent concerns with thrombotic side effects after vaccination with the AstraZeneca shot in Europe appear to be chance events, not casually related to the vaccine..
Most patients do not need to interrupt their anticoagulant before getting the vaccine. The COVID-19 vaccine is given as a shot into the deltoid muscle, just like the flu shot. The needle diameter used for injections is very fine, typically 22-25 gauge. It has been shown that intramuscular flu shots in patients on full-dose warfarin (Coumadin, Jantoven) do not increase the risk for bleeding at the site of the injection.
Similarly, it is reasonable to think that the risk for significant bleeding into the muscle is also not increased in a patient who takes a direct oral anticoagulant -- apixaban (Eliquis), dabigatran (Pradaxa), edoxaban (Savaysa), or rivaroxaban (Xarelto) -- or other anticoagulant like enoxaparin (Lovenox) or fondaparinux (Arixtra).
The FDA's COVID-19 vaccine factsheet calls for patients to tell their provider before getting the vaccine if they have a bleeding disorder or are on a blood thinner but does not provide any guidance for the provider. A few formal documents from societies and federal agencies provide useful input.
There is no benefit of giving a vaccine subcutaneously when it is really meant to be given intramuscularly, as that would not change the bleeding risk. That's true even in the patient with a bleeding disorder or on an anticoagulant, according to the CDC's Advisory Committee on Immunization Practices.
That group recommends scheduling vaccination prior to taking the blood thinner for the day, if possible. It also suggests using a fine-gauge needle (23-gauge or smaller) and applying firm pressure to the injection site, without rubbing, for at least 2 minutes. The patient or family should be given information on the risk for development of a hematoma.
The International Society on Thrombosis and Haemostasis (ISTH) recommends applying pressure to the injection site for longer -- at least 5 minutes -- to reduce the risk for bruising. It also suggests that patients on warfarin (Coumadin, Jantoven) wait until the INR drops below 4.0 before getting the injection.
For the patient who is on a blood thinner, I am a little more cautious than what is stated in the ISTH document. My suggestion is to use a 25 gauge needle or the smallest available caliber. I even suggest the patient ask the person injecting what gauge needle will be used and request a 25 gauge needle if the answer is any larger. However, if the 25 gauge is not available, the vaccination should go ahead with the smallest needle available.
I also recommend to consider skipping the morning dose of the blood thinner before the vaccination or the evening dose the day before vaccination in the case of a drug taken once daily in the evening.
Skipping one dose, or even two, may be particularly advisable for the patient who is on one of the blood thinners mentioned above plus another antithrombotic, whether aspirin, clopidogrel (Plavix), ticagrelor (Brilinta), or another anti-platelet drug.
If on warfarin, I recommend getting INR measured 2 to 5 days before the injection. If the INR is 3 or less, proceed with vaccination. If above 3, consider whether the patient should skip or decrease the next two warfarin doses or delay the immunization.