Clinical Trial

Immunogenicity of Twice-annual Influenza Vaccination in Older Adults in Hong Kong

Study acronym: RETAIN
Active, Not Recruiting Phase 4
View on ClinicalTrials.gov →
Record status
This record was last updated December 11, 2023 (before its estimated September 2025 completion). Its status may not reflect the trial's current state.
Summary
This study evaluates the immunogenicity of adding inactivated influenza vaccine with southern hemisphere (SH) formulation to standard once-annual influenza vaccination with northern hemisphere (NH) formulation in older adults in Hong Kong over 9 years. Half of participants will receive twice-annual influenza vaccination with NH and SH formulation, while the other half will receive once-annual influenza vaccination with NH formulation and a placebo.
Protocol Amendment History 5 amendments
This ClinicalTrials.gov record has been amended 5 times since 2016-11-03; most recent amendment 2023-12-08.
Status change: Recruiting → Active, Not Recruiting 2017-08-02
Status change: Not Yet Recruiting → Recruiting 2017-04-23
Trial Details
NCT Number NCT02957890
Lead Sponsor The University of Hong Kong
Collaborators: Centers for Disease Control and Prevention, Hospital Authority, Hong Kong
Conditions Influenza, Human
Enrollment 400 participants
Start Date 2016-11-18
Primary Completion 2025-09 (estimated)
Study Completion 2026-09 (estimated)
Updated on ClinicalTrials.gov 2023-12-11