Is it okay to give the influenza vaccine to people on anticoagulant (blood thinner) therapy, such as warfarin, aspirin, apixaban (Eliquis), or rivaroxaban (Xarelto)?

Yes, it is safe to give the influenza vaccine to people on blood thinners

Influenza vaccination can and should be administered to patients on anticoagulant therapy, including warfarin, aspirin, and DOACs like apixaban or rivaroxaban. The vaccine does not cause clinically significant changes in anticoagulation control, and the benefits of preventing influenza far outweigh any theoretical risks 1.

Route of Administration Matters

• Use intramuscular (IM) administration in the deltoid muscle for adults and older children, or the anterolateral thigh for infants and young children 1.
• The IM route has been adequately evaluated for safety and immunogenicity and is the recommended standard 1.
• Apply firm pressure at the injection site for 2 minutes after vaccination to minimize bruising risk in anticoagulated patients (general medical practice).

Evidence on Warfarin Interaction

Multiple prospective studies demonstrate no clinically significant interaction between influenza vaccine and warfarin:

• A 1992 ACIP guideline noted that influenza vaccination can theoretically inhibit warfarin clearance, but studies failed to show adverse clinical effects 1.
• A prospective study of 78 patients on stable warfarin showed no effect on INR control after vaccination, with no bleeding or thrombotic complications 2.
• Another study of 21 patients found prothrombin times remained in therapeutic range as often after vaccination as before, with no bleeding or thromboembolic problems 3.
• A systematic review through 2011 concluded there is no consistent, clinically relevant effect of influenza vaccines on INR in patients on chronic warfarin therapy 4.

No Special Monitoring Required

• Routine INR monitoring is not necessary after influenza vaccination in patients on stable warfarin therapy 2.
• The isolated case reports of INR changes are likely due to other factors rather than the vaccine itself 4.
• Minor bleeding events (nose bleeds, bruises) occurred at similar rates before and after vaccination 5.

DOACs and Antiplatelet Agents

• Clinical trials of DOACs (dabigatran, rivaroxaban, apixaban) allowed concomitant aspirin use, and the bleeding risk increase was similar to that seen with warfarin 1.
• There is no evidence suggesting influenza vaccine interacts with DOACs or antiplatelet agents.
• The vaccine is an inactivated product and cannot cause influenza or systemic coagulopathy 1.

Common Pitfalls to Avoid

• Do not withhold influenza vaccine from anticoagulated patients due to unfounded concerns about bleeding or INR changes.
• Do not use subcutaneous administration as a routine alternative—IM is the standard, evidence-based route 1.
• Do not confuse local soreness (occurs in <1/3 of vaccinees) with a contraindication to future vaccination 1.

Special Populations

• Patients on anticoagulation are often elderly or have cardiovascular disease, making them high-priority candidates for influenza vaccination 1.
• Healthcare providers caring for anticoagulated patients should themselves be vaccinated to reduce transmission risk 1.