This study explores the hypothesis that the use of an adjuvanted influenza vaccine in the elderly will produce greater vaccine effectiveness in their group.

To evaluate the effectiveness of adjuvanted trivalent inactivated influenza vaccine in the elderly (aged ≥ 65 years) through the reduction in relative risk of microbiologically confirmed influenza illness

Inclusion Criteria:

1.Elderly tested for influenza as part of routine clinical care in the Lower Mainland and on Vancouver Island during the influenza season.

Cases: Proven influenza diagnosed on naso-pharyngeal swab via PCR Controls: Elderly with influenza-like-illness testing negative for influenza during the influenza season.

Exclusion Criteria:

1. Known immunodeficiency disorders (including HIV)
2. Current or recent (within 90 days prior to first dose of influenza vaccine) immunosuppressive treatment including chronic oral steroids (1mg/kg for > 4 weeks), cytotoxic chemotherapy, radiation therapy, other immunosuppressive drug and biologic agents Note: Use of topical or inhalant corticosteroids is acceptable.
3. Administration of immunoglobulins during the study period;

All elderly over 65 years in the lower mainland of British Columbia presenting with an influenza-like-illness