Effect of Oral Supplement on Influenza Vaccine Long-term Response

This is a follow-up study of a previously completed randomized controlled trial (NCT06827873) that investigated the effects of oral supplements on influenza vaccine response in adults aged 60-70 years. The original study was completed in April 2025, with participants receiving either TUDCA (Tauro Ursodesoxy Cholic Acid) supplementation, fatty acid supplementation, or placebo during influenza vaccination.

The primary objectives of this follow-up study are to:

1. Evaluate the durability of vaccine-induced antibody responses approximately 8 months post-vaccination 2. Assess the persistence of immune memory cells, particularly long-lived plasma cells and memory B cells 3. Compare long-term immune responses between the TUDCA supplementation group and placebo group

This observational follow-up involves a single visit where participants will:

1. Provide one blood sample for antibody and immune cell analysis 2. No intervention or vaccination will be administered

The study will specifically focus on B cell subsets through flow cytometry analysis, including total B cells, memory B cells, plasma cells, and long-lived plasma cells. This research aims to determine whether TUDCA supplementation can enhance the durability of vaccine-induced immunity in older adults.