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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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  • 1Dipartimento di Area Critica Medico-Chirurgica, Centro di Riferimento Regionale per la Trombosi, Azienda Ospedaliera Careggi, Universit√† degli studi di Firenze, Italy. polida@ao-careggi.toscana.it


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.

[PubMed - indexed for MEDLINE]
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