Universal anti-hepatitis-B vaccination of infants and adolescents was implemented in Italy in 1991.
Professor Alessandro Zanetti and colleagues from Italy undertook a multicenter study in previously vaccinated individuals.
The research team assessed the duration of immunity and need for booster, over 10 years after vaccination.
The team included 1212 children and 446 Italian Air Force recruits vaccinated as infants and adolescents, respectively.
The researchers measured the concentrations of antibodies to hepatitis-B surface antigen.
The presence of antibodies to hepatitis-B core antigen at enrolment were also measured, however, postimmunization values were not available.
Individuals positive for hepatitis-B core antigen were tested for hepatitis B surface antigen and hepatitis B viral DNA.
|Hep-B surface antigens were retained in 64% of children and 89% of recruits |
Individuals with hepatitis-B surface antigen concentrations at 10 IU/L or more were regarded as protected.
The team gave those with antibody less than 10 IU/L a booster dose and retested them 2 weeks later.
Individuals showing postbooster hepatitis-B surface antigen concentrations of less than 10 IU/L were offered 2 additional vaccine doses.
The researchers then retested those with 2 additional vaccine doses 1 month after the third dose.
Protective hepatitis-B surface antigen concentrations were retained in 64% of children and 89% of recruits.
The research team recorded antibody amounts of less than 10 IU/L in 36% of children and 11% of recruits.
The team noted that 1 child and 4 recruits were positive for hepatitis-B core antigen, but negative for hepatitis B surface antigen and hepatitis B viral DNA.
Antibody concentrations were higher in recruits than in children.
The researchers found that 97% of children and 96% of recruits who received a booster showed an anamnestic response.
However, the team noted that 3% of children and 4% of recruits remained negative for hepatitis-B surface antigen or had antibodies of less than 10 IU/L.
Prebooster and postbooster antibody titres were strongly correlated with each other in both groups.
All individuals given 2 additional vaccine doses showed hepatitis-B surface antigen amounts of more than 10 IU/L at 1 month after vaccination.
Professor Zanetti's team commented, “Strong immunological memory persists more than 10 years after immunisation of infants and adolescents with a primary course of vaccination.”
“Booster doses of vaccine do not seem necessary to ensure long-term protection.”