INFLUENZA VACCINATION AND WARFARIN ANTICOAGULATION - A COMPARISON OF SUBCUTANEOUS AND INTRAMUSCULAR ROUTES OF ADMINISTRATION IN ELDERLY MEN

Study Objectives. To determine if subcutaneous administration of influ enza vaccine is as immunogenic as the intramuscular route, and to eval uate the frequency of local adverse events associated with both routes in elderly anticoagulated men. Design. Single-blind, prospective stud y of consecutively enrolled subjects. Setting. Ambulatory clinic at a university-affiliated Veterans Affairs medical center. Patients. Twent y-six men age 60 years or older, receiving therapeutic dosages of warf arin. Interventions. Subjects were randomized to receive either intram uscular or subcutaneous injection of a standard trivalent influenza va ccine. Measurements and Main Results. Serum antibody titers to the vac cine's components were measured at baseline, and 6 weeks and 4 months after vaccination. Both routes of administration induced comparable se rum antibody titers. There were no differences in adverse events at ad ministration sites between routes of administration. Conclusions. Elde rly individuals are able to mount an immune response to influenza vacc ine and produce antibody concentrations deemed protective. The routes of administration are similarly effective at inducing an immune respon se. The intramuscular route in anticoagulated elderly men does not com monly result in local bleeding complications.