Safety and immune response to a challenge dose of hepatitis B vaccine in healthy children primed 10 years earlier with hexavalent vaccines in a 3, 5, 11-month schedule: An open-label, controlled, multicentre trial in Italy

Abstract Background and aims The strategy of vaccinating infants to prevent hepatitis B virus infection in adolescence or adulthood requires durable immunity. This study investigated responses to a challenge dose of monovalent hepatitis B vaccine in children primed with three doses of either Hexavac® or Infanrix hexa® 10 years earlier during infancy. Methods This open-label, controlled, multicentre study conducted in Italy, enrolled 751 healthy pre-adolescents (aged 11–13 years) who were given either Hexavac (n = 409) or Infanrix hexa (n = 342) at 3, 5 and 11 months of life. All participants received a challenge dose of a monovalent hepatitis B vaccine (HBVaxPro® 5 µg). The concentrations of antibodies to hepatitis B surface antigen (anti-HBs) were measured before and 1 month after the challenge dose. The analysis was descriptive and no formal hypothesis was tested. Results One month post-challenge, 331 participants in the Hexavac cohort [83.6%, 95% CI: 79.6; 87.1] and 324 in the Infanrix hexa cohort [96.4%, 95% CI: 93.8; 98.1] had anti-HBs concentrations ≥10 mIU/mL. Before the challenge dose, an anti-HBs concentration of ≥10 mIU/mL was found in 94 children in the Hexavac cohort [23.9%, 95% CI: 19.7; 28.4] and in 232 children in the Infanrix hexa cohort [69%, 95% CI: 63.8; 74.0]. Among children with a pre-challenge anti-HBs concentration of Conclusions These data confirm that immune memory persists in a high percentage of children (>80%) at least 10 years after a two-dose primary and booster vaccination schedule with a hexavalent vaccine (Hexavac or Infanrix hexa). Trial registration: EudraCT Number: 2013-001602-28; clinicaltrials.gov: NCT02012998