Meet any of the following criteria are eligible to join the study:
70-79 years of age
DID NOT suffer any adverse reaction after flu shot in previous years
Willing to receive 2 seasonal flu shots every year in 2017-2021
Meet any of the following criteria are not eligible to join the study:
- Signs of dementia or significant cognitive impairment and not competent to give consent.
- Medical conditions not suitable to receive inactivated influenza vaccines such as severe allergic reaction after previous dose of any influenza vaccine; or to a vaccine component, including egg protein; moderate or severe acute illness with or without fever after any previous influenza vaccination; or a history of Guillain-Barré syndrome (GBS) within 6 weeks of previous influenza vaccination.
- Report medical conditions not suitable to receive intramuscular injection including bleeding disorders and habitually taking anticoagulants (with the exception of antiplatelets such as aspirin).
- Medical conditions not suitable to receive inactivated influenza vaccines as determined by a clinician.