Long-term Immunogenicity of L-HAV Vaccine Among Healthy Thai Children and Adolescents

Launched by CHIANG MAI UNIVERSITY · Jun 16, 2025

Keywords

ClinConnect Summary

This clinical trial is studying how well a single dose of the live-attenuated hepatitis A vaccine (L-HAV) protects healthy Thai children and teenagers against hepatitis A over a long period. Hepatitis A is a common liver infection spread through contaminated food or water, and vaccines can help prevent it. In Thailand, two types of hepatitis A vaccines are available: one given in two doses (inactivated vaccine) and another given as a single dose (live-attenuated vaccine). This study focuses on children and adolescents who already received one dose of the live-attenuated vaccine about a year ago, to see how well their bodies are still protected.

To join the study, participants must be Thai children or teenagers aged between roughly 1.5 and 18 years who were part of a previous related vaccine study and got the live-attenuated vaccine. They and their caregivers need to agree to take part by signing a consent form. People who have recently been sick, have had hepatitis A before, received extra hepatitis A vaccines since the last study, or have certain symptoms like fever or jaundice won’t be eligible. Participants can expect to have their blood tested to check their immunity against hepatitis A and will be monitored to make sure the vaccine remains safe and effective over time. This study will help doctors understand how long the single-dose vaccine can protect children and could guide future vaccine programs in Thailand.

Gender

ALL

Eligibility criteria

• Inclusion Criteria:
• • Thai children and adolescents who previously participated in the previous RCT study
• • Previously randomized to receive one dose of L-HAV vaccine within the past 1 year (+/- 3 months)
• • Participants and/or caregivers gives written inform consent/assent form
• Exclusion Criteria:
• • History of acute illness within 4 weeks prior to study enrollment
• • Has a history of illness or a diagnosis consistent with hepatitis A after receiving the live attenuated hepatitis A vaccine as part of participation in a previous research study
• • Has a history of receiving any additional hepatitis A vaccine after participating in the previous research study
• • Presence of fever (body temperature ≥38.0°C), jaundice, or yellowing of the eyes within 4 weeks prior to study enrollment
• • Have any condition that, in the opinion of the site investigator, would compromise the subject's ability to participate in the study