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

Long-term Immunogenicity of Lived-attenuated Hepatitis A Virus Vaccine Among Healthy Thai Children and Adolescents

Status

Active, not recruiting

Phases

Unknown

Study type

Observational

Source

ClinicalTrials.gov

Registry ID

NCT07032610

Enrollment

Registered

2025-06-24

Start date

2025-06-26

Completion date

2026-07-31

Last updated

2026-05-22

For informational purposes only — not medical advice. Sourced from public registries and may not reflect the latest updates. Terms

Conditions

Hepatitis A, Hepatitis A Virus, Vaccine-Preventable Diseases

Keywords

Live-attenuated hepatitis A vaccine, Immunogenicity, Seropositive rate

Brief summary

Hepatitis A virus (HAV) remains a common infection among Thai children. Two types of HAV vaccines are available in Thailand: an inactivated vaccine (I-HAV, administered in two doses 6 months apart) and a live-attenuated vaccine (L-HAV, administered as a single dose). However, neither vaccine is currently included in Thailand's Expanded Programme on Immunization (EPI). In 2024, a randomized, active-controlled, open-label, non-inferiority trial was conducted to compare the immunogenicity and safety of the two-dose I-HAV with the single-dose L-HAV in healthy Thai children and adolescents aged 18 months to 18 years. This study aims to evaluate the long-term seropositive rate and immunogenicity of anti-HAV antibodies in this population following a single dose of L-HAV.

Detailed description

Hepatitis A virus (HAV) infection remains one of the most common causes of viral hepatitis among children and adolescents in developing countries, including Thailand. The virus is primarily transmitted through the ingestion of contaminated food or water, or through direct contact with an infected person. HAV typically causes acute hepatitis, ranging from mild illness to severe fulminant hepatitis (acute liver failure), but it does not lead to chronic liver disease. Vaccination is a highly effective strategy to prevent HAV infection and its serious complications. Currently, two types of HAV vaccines are available in Thailand: (1) the inactivated HAV vaccine (I-HAV), which is administered in two doses six months apart and is approved for use in children aged 12 months and older; and (2) the live-attenuated HAV vaccine (L-HAV), administered as a single dose and approved for children aged 18 months and older. However, neither vaccine has been included in Thailand's Expanded Programme on Immunization (EPI), resulting in suboptimal vaccination coverage across the country. In 2024, the investigators conducted a randomized, active-controlled, open-label, non-inferiority trial to compare the immunogenicity and safety of the two-dose I-HAV regimen with the single-dose L-HAV in healthy Thai children and adolescents aged 18 months to 18 years. The present study aims to assess the long-term seropositive rate and immunogenicity of anti-HAV antibodies among these participants following a single dose of L-HAV.

Interventions

None listed

Study design

Observational model

CASE_ONLY

Time perspective

CROSS_SECTIONAL

Eligibility

Sex/Gender

ALL

Age

18 Months to 20 Years

Healthy volunteers

Yes

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

Design outcomes

Primary

Measure	Time frame	Description
Anti-HAV seropositivity rate	1 year after L-HAV vaccination	Anti-HAV seropositivity rate following a single L-HAV vaccine
Anti-HAV antibody level	1 year after L-HAV vaccination	Geometric mean concentration (GMC) of anti-HAV antibodies following a single L-HAV vaccine

Countries

Thailand

Contacts

STUDY_CHAIRTavitiya Sudjaritruk, MD, PhD

Department of Pediatrics, Faculty of Medicine, Chiang Mai University

PRINCIPAL_INVESTIGATORNatchaya Kunanitthaworn, MD