COVID-19 Vaccination While on a Blood Thinner

A. Is it ok for me to get the COVID-19 vaccine?

• Yes, it is ok to take for pretty much all individuals, no matter whether they have a clotting disorder (=thrombophilia), have had a blood clot (DVT or PE), or are on a blood thinner. Reasons NOT to get the vaccine have to do with allergies (reference 1), but NOT with the fact that a patient has had a clot or is on a blood thinner. 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. Patients should NOT avoid the COVID vaccination because they are on a blood thinner.
  

B. Do I need to interrupt my blood thinner before getting the vaccine?

• No.  Most patients do NOT need to interrupt the blood thinner.  The COVID-19 vaccine is given as a shot into the muscle (deltoid muscle) in the arm (= intra-muscular = i.m.), just as the flu shot. The needle diameter used for injections is very small/fine, typically 22-25 gauge (reference 2).  It has been shown that i.m. flu shots in patients on full-dose warfarin (= Coumadin®, Jantoven®) do NOT increase the risk for bleeding at the site of the injection (reference 3). Similarly, it is reasonable to think that the risk for significant bleeding into the muscle is also not increased in a patient who takes Eliquis®, Pradaxa®, Savaysa®, Xarelto®, or Lovenox® (enoxaparin) or Arixtra® (= fondaparinux).  There is no benefit of giving a vaccine into the skin (subcutaneously; s.c.) when it is really meant to be given intramuscularly as that does not change the bleeding risk [reference 4].
•  Four formal documents – from societies and federal agencies – are worth mentioning and referencing:
  • CDC (Advisory Committee on Immunization Practices = ACIP) states in their section on ‘Vaccinating Persons with Increased Bleeding Risk’ states (reference 5):
    • A vaccine that is meant to be given i.m. should be given i.m. (not via a different injection method)even in the patient with a bleeding disorder or on an anticoagulant.
    • A fine-gauge needle (23-gauge or smaller caliber; explanation: the higher the gauge number, the smaller the needle; smallest needle is 25 gauge) should be used.
    • Firm pressure should be applied 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 (a knot underneath the skin from a bleed into the soft tissue).
    • If possible, vaccination should be scheduled prior to the use of the blood thinner.
  • ISTH: The International Society on Thrombosis and Haemostasis (ISTH) appropriately states that:
    • patients on blood thinners receiving the vaccine have “a risk of bruising at the injection site, but we do not anticipate any serious effects related to anticoagulation”
    • pressure for at least 5 minutes should be applied to the injection site to reduce the risk for bruising;
    • patients on warfarin (coumadin®, Jantoven®) with a high INR (4.0 or above) should wait until the INR drops below 4.0 before getting the injection (reference 6).
  • UKMi (United Kingdom Medicines Information)[reference 7] – a British summary of  the topic.
  • FDA: The COVID-19 vaccine ‘Fact Sheet’ (reference 1) from the FDA states that patients should mention to their provider before getting the vaccine if they have a “bleeding disorder or are on a blood thinner”. However, the ’Fact Sheet’ does not provide guidance what the provider is to tell the patient or what the patient on a blood thinner should do.

C. My conclusions:

• Yes, do get the vaccine. Patients with DVT or PE, thrombophilia or on blood thinners can (and should) get COVID-19 vaccinated. Don’t avoid the immunization because you are on a blood thinner.
• The shot should be given into the muscle, not into the skin. (i.e. not s.c.)
• The patient who is on a blood thinner: For the patient on a blood thinner, I am a little more cautious than what is stated in the ISTH document mentioned above [reference 6]. My suggestion:
  • 25 gauge needle: The smallest possible needle size should be used, preferably 25 gauge size.  I suggest the patient ask the person injecting: “What gauge needle are you using for my injection?”; if it is not a 25 gauge, request a 25 gauge needle (Explanation: the higher the gauge number, the smaller and, therefore, more suitable, the needle size; 22 gauge is too big). If the 25 gauge needle is not available, settle for the next size closest to gauge 25.
  • Consider skipping one dose of the blood thinner.  If a patient is on Eliquis®, Pradaxa®, Savaysa®, Xarelto®, Lovenox® (enoxaparin) or Arixtra® (= fondaparinux), it is reasonable to skip one dose of the medication before the vaccination – either (a) the morning dose on the day of the procedure; or, (b) if patient takes Xarelto®, Lovenox® or Arixtra® only once daily in the evening, skipping the dose in the evening of the day prior to the vaccination.
  • Skipping one (or two) dose(s) may be particularly advisable for the patient who is on one of the  blood thinners mentioned above PLUS Aspirin, Plavix®, Brillinta® or another anti-platelet drug.
  • If on warfarin:
    • Get an INR 2-5 days before the injection.
    • Go ahead with the immunization if the INR is 3 or less.
    • If INR is above 3, your warfarin provider (doctor, pharmacist, nurse) should tell you whether you should skip or decrease the next 2 warfarin doses, or delay the immunization.
  • Put pressure on the vaccination injection site for at least 5 minutes.
• If you have some other reason to be at higher risk for bleeding (such as having low platelets, or liver or kidney disease), talk to your medical provider how to safely get the vaccination.

References

1. https://www.fda.gov/media/144414/download – “Fact sheet about COVID-19 vaccine” from the FDA, version Dec 2020.
2. https://www.cdc.gov/vaccines/hcp/admin/downloads/vaccine-administration-needle-length.pdf
3. Raj G et al. Safety of intramuscular influenza immunization among patients receiving long-term warfarin anticoagulant therapy. Arch Internal Med 1995;155:1529-31.
4. Casajuana J et al. Safety of intramuscular influenza vaccine in patients receiving oral anticoagulation therapy: a single blinded multi-centre randomized controlled clinical trial. BMC Blood Disorders 2008, 8:1
5. https://www.cdc.gov/vaccines/hcp/acip-recs/general-recs/special-situations.html – version Nov 2020.
6. https://www.worldthrombosisday.org/covid-19-thrombosis/
7. https://www.sps.nhs.uk/wp-content/uploads/2018/09/UKMI_QA_IM-inj-anticoag_partial-update_Sept2018.pdf . Version July 2018