Estimate the Safety and Effectiveness of Adjuvanted Influenza Vaccine Among Asian Elderly People When Compared to Non-adjuvanted Vaccines

Inclusion Criteria: * Adults aged 65 years or above * Presence of at least 1 chronic medical condition associated with increased risk of complicated influenza, including hypertension, chronic obstructive pulmonary disease (group A, B, E), asthma, congestive heart failure (ACC/AHA stage A, B, C, D), coronary arterial disease, diabetes mellitus, chronic liver disease (Child-Pugh score A, B, C) or chronic kidney disease (stage 1\~4), neuromuscular disorders, hematological or solid organ malignancies, recipient of hematopoietic stem cell transplantation or solid organ transplantation. Exclusion Criteria: * Contraindications to influenza vaccination including history of severe adverse event after vaccination, such as anaphylaxis or Guillain-Barré Syndrome, or a severe bleeding tendency * Prior receipt of influenza vaccination during the current flu season. * Determination by the Principal Investigator (PI) that the participant is ineligible for enrollment based on clinical assessment.