Comparison of 4 Influenza Vaccines in Seniors

Inclusion Criteria: * Written informed consent provided by the subject, who can be male or female * Subjects who the investigator believes can and will comply with the requirements of the protocol (i.e. return for follow-up visits, record safety observations and able to converse with study personnel including by personal telephone) * Age 65 years or older at Visit 1 * Generally good health (stable chronic conditions acceptable), living independently or with minimal assistance (Clinical Frailty score 1-5) (33) and able to attend clinic appointments * Receipt of at least one dose of TIV within the previous 2 influenza seasons, documented by written record or attested by a confident personal recollection. This refers to the trivalent seasonal vaccine, not the H1N12009 pandemic vaccine. Exclusion Criteria: * receipt of non-study influenza vaccine for 2011-12 * receipt of any live vaccine within 4 weeks or inactivated vaccine within one week of Visit 1 or planned administration of any non-study vaccines between Visits 1 and 2 * systemic hypersensitivity to influenza vaccine, hen's eggs or other vaccine constituent (eg neomycin sulphate, kanamycin, formalin) * severe reaction to any previous influenza vaccine or vaccine component * bleeding disorder, including anticoagulant therapy or thrombocytopenia, that contraindicates IM injection or blood collection (does not include daily low-dose ASA). * incapacity to provide fully informed consent or be attentive to follow-up observations, resulting from cognitive impairment, abuse of alcohol, drug addiction * lack of telephone access, inadequate fluency in English (or French in applicable jurisdictions), uncertain availability during the 3 week study participation period or for the 6 month follow-up visit * immune compromise resulting from disease or immunosuppressive systemic medication use within 3 months of V1 * receipt of blood or blood product within 3 months of V1 * unstable medical condition, as indicated by a requirement for hospitalization or a substantial medication change to stabilize said condition within previous 3 months * Clinical Frailty score of 6-7 (moderately frail or severely frail) * history of Guillain-Barré syndrome