The effectiveness of the standard influenza vaccine in older adults is often not as good as in young population. Besides, the adjuvanted, high-dose and recombinant influenza vaccines have been approved by the United States Food and Drug Administration (FDA) or European Medicines Agency (EMA), have not yet been introduced for common use despite the growing evidence of their effectiveness. In this regard, the School of Public Health of the University of Hong Kong cooperates with Centers for Disease Control and Prevention, are inviting older adults to participate this study to assess the immunogenicity of annual seasonal influenza vaccination, will be assigned to receive one of the four influenza vaccines every year in the coming 4 years, using different combination of these potent vaccine options with standard vaccine to find the most suitable vaccination strategy for Hong Kong older people.

According to the primary analysis conducted in the (PIVOT) study, the more potent influenza vaccine have shown to induce higher antibody response among the participated elderly communities in comparison to the standard vaccine. To widen the scope of the study, we would like to invite an additional of 550 elderly participants in the year 2019-2020 as an extension. Those who are eligible for the study will be invited for vaccination annually in the upcoming two years. In order to show our great appreciation for participation, each participant will also receive a free body-check and coupon reimbursement.