Safety of the Intramuscular Route of the Anti-Flu Vaccine in Patients Receiving Oral Anticoagulation Therapy

Until now, the best administration route of the anti-flu vaccine for patients receiving long term oral anticoagulation therapy has been the subcutaneous one; the intramuscular route has not been recommended because it may increase the risk of muscular haematoma. Although this practice is widely extended, no significant differences between the safety of both routes have been found. Some authors, analysing a small group of patients, affirm that the anti-flu vaccine can be administered safely by the intramuscular route on patients receiving long term oral anticoagulation therapy, while a previous opinion article recommended the subcutaneous route without any scientific evidence. Due to this, the investigators have done a clinical trial with the aim of determining the safety and effectiveness of the flu-vaccine intramuscular route in patients receiving long term oral anticoagulation therapy and also to analyse the possible interactions between the vaccine and the oral anticoagulant treatment.