A booster shot against hepatitis B may not be necessary because infants and teens who are vaccinated against hepatitis B are protected for 10 years after the vaccination, according to Italian researchers.

Viral hepatitis B is the leading cause of acute and chronic liver disease worldwide. About 2 billion people around the world have been infected with hepatitis B, says the World Health Organization. Currently, 168 countries have universal infant or adolescent hepatitis B vaccination programs.

Until now, it wasn't clear if vaccinated children needed booster shots to sustain their immunity to hepatitis B infection.

Reporting in this week's issue of The Lancet, the researchers studied whether concentrations of antibodies against hepatitis B were still present in 1,212 children and 446 Italian Air Force recruits who received hepatitis B vaccinations as infants and adolescents, respectively.

The study found that 64 percent of the children and 89 percent of the recruits still had protective concentrations of antibodies. The results indicate that infant and adolescents immune systems can recall responding to hepatitis B more than 10 years after immunization.

"In light of our findings, the use of routine booster doses of hepatitis B vaccine does not seem necessary to maintain long-term protection in immunocompetent individuals vaccinated as infants and teenagers," researcher Alessandro Remo Zanetti of the Institute of Virology in Milan, said in a prepared statement.