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Blood Coagul Fibrinolysis. 2002 Jun;13(4):297-300.

Need of more frequent International Normalized Ratio monitoring in elderly patients on long-term anticoagulant therapy after influenza vaccination.

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Dipartimento di Area Critica Medico-Chirurgica, Centro di Riferimento Regionale per la Trombosi, Azienda Ospedaliera Careggi, Università degli studi di Firenze, Italy.


Previous findings suggest the safety of influenza vaccination for patients on oral anticoagulant therapy (OAT). However, some studies reported a moderate reduction or increase of the anticoagulation. We assessed the effect of influenza vaccination on anticoagulation levels. Seventy-three patients on stable long-term OAT were recruited. Patients were compared with a control group of 72 patients observed during the same period. No differences in the anticoagulation levels were found in patients and in controls during the 3 months before and after the vaccination. However, in patients older than 70 years we observed a reduction of anticoagulation intensity achieved in the month after the vaccination, with a prolonged time spent below the therapeutic range (10% before and 27% after, P = 0.001), and this behaviour was still observed 3 months after vaccination. Influenza vaccination is safe in patients on OAT, but it is associated with a slight reduction in warfarin effect in the elderly, suggesting the need of more frequent International Normalized Ratio monitoring after vaccination in these subjects.

[Indexed for MEDLINE]

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