This study is a prospective, multicenter, randomized, evaluator-blinded, controlled, parallel-group study of 3 licensed seasonal influenza vaccine products conducted in seniors, with a 4th vaccine included in a substudy of cellular immune responses.

Ambulatory adults 65+ years of age, in good health or with stable health conditions, given TIV within the past 2 years, will be recruited in multiple Canadian centers. Subjects can be dwelling in the community or in centers providing minimal assisted living support. A total of 930 subjects will be enrolled.