Hepatitis A virus (HAV) vaccine is an effective strategy to prevent natural HAV infection. In Thailand, there are 2 types of HAV vaccine available, including inactivated HAV vaccine and live-attenuated HAV vaccine. This study aims to compare the immunogenicity and safety of inactivated and lived-attenuated HAV vaccine among Thai healthy children and adolescents age 18 months to 18 years.

Hepatitis A virus (HAV) infection is one of the common cause of viral hepatitis in children and adolescents in developing countries, including Thailand. This virus is easily transmitted through ingestion of contaminated food and water or through direct contact with an infectious person. Generally, HAV causes acute hepatitis, ranging mild illness to severe fulminant hepatitis (acute liver failure), but does not cause chronic liver disease. HAV vaccine is an effective strategy to prevent natural HAV infection as well as serious consequences of the illness.

Currently, there are 2 types of HAV vaccine available in Thailand, including (1) inactivated vaccine (I-HAV) which is recommended for 2 doses, 6 months apart and is approved for children age 1 year and above; and (2) live-attenuated vaccine (L-HAV) which is recommended for 1 dose and is approved for children age 18 months and above. However, these vaccines have not included in the Thailand Expanded Programme on Immunization (EPI) yet. Thus, vaccination coverage rate is suboptimal in the country. Moreover, the information regarding immunogenicity and safety of both vaccines is limited.

This is a randomized, active-controlled, open-label, non-inferiority trial which aims to compare the immunogenicity and safety of a marketed inactivated (I-HAV) and a live-attenuated HAV vaccine (L-HAV) among Thai healthy children and adolescents age 18 months to 18 years. This study will provide important information about the immunogenicity and safety profiles of both vaccines in Thai healthy youth as well as demonstrate the associated factors of HAV vaccine-elicited immunity in this population.

Inclusion Criteria:

• Age between 18 months and 18 years
• Has healthy status
• Has no history of hepatitis A infection or previous hepatitis A disease
• Has never received hepatitis A vaccine (from vaccine booklet or parental history)
• Participants and/or caregivers gives written inform consent/assent form

Exclusion Criteria:

• Has acute illness within 4 weeks before enrollment
• Has fever with jaundice within 4 weeks before enrollment
• Has underlying disease of thrombocytopenia, coagulopathy, hemophilia A or B, neurologic disease, immunocompromised condition, chronic liver disease, chronic hepatitis B or C infection
• Has received immunosuppressive agents or immunomodulatory agents, corticosteroid >2 mg/kg/day or 20 mg/day within 6 months before enrollment
• Has received blood or blood component, or intravenous immunoglobulin within 6 months before enrollment
• Has received any lived-attenuated vaccine within 30 days before enrollment
• Has history of severe allergy to vaccine or vaccine component, including aluminum hydroxide, 2-phenoxyethanol, neomycin, formaldehyde, gentamicin sulfate, or has history of anaphylaxis or severe allergic reactions following vaccination
• Women planning for pregnancy, pregnant women or lactating women
• Women in childbearing age who cannot use contraceptive methods during study participation
• Is concurrently involved in other clinical trials in which receiving an investigational vaccine or study drug as part of study participation
• Have any condition that, in the opinion of the site investigator, would compromise the subject's ability to participate in the study

There is not a plan to make individual participant data (IPD) available for this study.