Need of more frequent International Normalized Ratio monitoring in elderly patients on long-term anticoagulant therapy after influenza vaccination.
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.
Poli
D
D
Dipartimento di Area Critica Medico-Chirurgica, Centro di Riferimento Regionale per la Trombosi, Azienda Ospedaliera Careggi, Università degli studi di Firenze, Italy. polida@ao-careggi.toscana.it
Chiarugi
L
L
Capanni
M
M
Antonucci
E
E
Abbate
R
R
Gensini
G F
GF
Prisco
D
D
D000368:Aged; D000925:Anticoagulants / Q000097:blood* / Q000627:therapeutic use; D016022:Case-Control Studies; D004347:Drug Interactions; D016903:Drug Monitoring / Q000592:standards*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007252:Influenza Vaccines / Q000494:pharmacology*; D019934:International Normalized Ratio; D008297:Male; D008875:Middle Aged; D013997:Time Factors; D014859:Warfarin / Q000097:blood / Q000627:therapeutic use
D000925:Anticoagulants; D007252:Influenza Vaccines; D014859:Warfarin