A non-blinded two-arm parallel randomized controlled trial will be conducted. Inclusion criteria are: 1) aged ≥65 years, 2) having Hong Kong ID, 3) Chinese speaking, 4) willing to be followed up by telephone, 5) having a smartphone, and 6) have not received SIV for the incoming flu season. Exclusion criteria include: 1) cognitive impairment, blindness or deafness, 2) not able to communicate with others effectively, and 3) with known contradictions of SIV (allergic to previous SIV, diagnosed/suspected egg allergy, with bleeding disorder or on warfarin). A total of 396 participants will be randomly assigned to either the intervention group (n=198) or the control group (n=198). Intervention group will watch an online health promotion video tailored to their current stage of change related to SIV uptake once every two weeks for four times (at week 0, 2, 4, and 6).

Participants in the control group will watch a same online video providing general advices related to SIV at week 0, 2, 4, and 6. All participants will be followed up by telephone 3 and 6 months after the baseline survey.

Inclusion Criteria:

• Aged ≥65 years,
• Having Hong Kong ID
• Chinese speaking
• Willing to be followed up by telephone
• Having a smartphone
• Have not received seasonal influenza vaccination for the incoming flu season

Exclusion Criteria:

• Cognitive impairment, blindness or deafness,
• Not able to communicate with others effectively
• With known contradictions of seasonal influenza vaccination listed by the Centre for Health Protection (allergic to previous SIV, diagnosed/suspected egg allergy, with bleeding disorder or on warfarin)