Immunogenicity and Safety of I-HAV in Healthy Thai Children and Adolescents Lacking Protective Antibody After L-HAV

Summary

Hepatitis A virus (HAV) remains a common infection in Thai children. Two HAV vaccines are available: inactivated vaccine (I-HAV, 2 doses) and live-attenuated vaccine (L-HAV, single dose), but neither is included in Thailand's national immunization program. Our previous randomized, active-controlled, open-label, non-inferiority trial trial found that some participants remained seronegative after one L-HAV dose (anti-HAV IgG \<1 S/CO) (preliminary data). This study aims to evaluate the immunogenicity and safety of an additional dose of I-HAV in healthy Thai children and adolescents who did not develop protective antibody levels after a single dose of L-HAV.

Eligibility

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 (+/- 2 months)
* Have not demonstrate a seropositivity against HAV (anti-HAV IgG \<1 S/CO) at 1 month after L-HAV vaccination
* 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
* Has underlying conditions including thrombocytopenia, coagulopathy, hemophilia A or B, neurological disorders, immunodeficiency disorders, chronic liver disease, or chronic hepatitis B or C infection
* Has received immunosuppressive agents, immunomodulatory agents, or high-dose corticosteroids (greater than 2 mg/kg/day or more than 20 mg/day) for more than 14 consecutive days within 6 months prior to study enrollment
* Has received blood products or blood components, including immunoglobulins, within 6 months prior to study enrollment
* Has received other live vaccines within 30 days prior to study enrollment
* Has history of allergy to vaccines or any vaccine components, such as aluminum hydroxide, 2-phenoxyethanol, neomycin, formaldehyde, or gentamicin sulfate, or has history of severe allergic reactions (e.g., anaphylaxis) to any vaccines
* 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

Conditions4

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