Immunogenicity, safety, and interchangeability of two inactivated hepatitis A vaccines in Chilean children

Area of Science:

• Immunology
• Vaccinology
• Pediatrics

Background:

• Hepatitis A virus (HAV) infection poses a significant public health concern, necessitating effective vaccination strategies.
• Pediatric vaccination is crucial for establishing herd immunity and long-term protection against HAV.
• Comparing the immunogenicity and safety of different pediatric hepatitis A vaccines is essential for optimizing public health recommendations.

Purpose of the Study:

• To compare the immunogenicity, safety, and interchangeability of two pediatric hepatitis A vaccines: Avaxim 80U-Pediatric and Havrix 720.
• To evaluate the antibody responses and reactogenicity following single and double doses of these vaccines in Chilean children.
• To determine if Avaxim 80U-Pediatric can be used to complete a vaccination schedule initiated with Havrix 720.

Main Methods:

• A randomized trial involving 332 HAV-seronegative children aged 1 to 15 years.
• Participants received two doses of Avaxim, two doses of Havrix, or a sequential schedule of Havrix followed by Avaxim, 6 months apart.
• Anti-HAV antibody titers were measured at various time points, and vaccine reactions were monitored through parental reports.

Main Results:

• High seroconversion rates were observed after the first dose (99.4% for Avaxim, 100% for Havrix).
• Two-dose schedules of either vaccine or the sequential Havrix/Avaxim regimen elicited robust booster responses, with geometric mean concentrations (GMCs) significantly increasing.
• Both vaccines demonstrated favorable safety profiles, with local and systemic reactions reported by a similar proportion of participants, and fewer reactions after the second dose.

Conclusions:

• No significant difference in seroconversion rates was found after a single vaccine dose.
• Both Avaxim 80U-Pediatric and Havrix 720 are well-tolerated and immunogenic, supporting their recommendation for routine vaccination of Chilean children.
• The interchangeability of these vaccines is supported, with Avaxim 80U-Pediatric suitable for completing a Havrix 720 schedule.