The hepatitis B virus is common. About 2 billion people worldwide have been infected, and more than 350 million of them have lifelong (chronic) infections, according to the World Health Organization (WHO).
The virus spreads through blood or body fluids. For instance, it can spread through sex, shared drug needles, or from an infected mother to her baby during birth.
Vaccination doesn't cure hepatitis B. However, it's 95% effective at preventing the development of chronic hepatitis B infection, states the WHO's web site.
Chronic hepatitis B infection is most common in Africa, Asia, the Amazon region, and the southern parts of Eastern and Central Europe. It's less common in Western Europe and North America, states the WHO.
Zanetti's study included about 1,200 Italians who had received the hepatitis B vaccine in infancy. An additional 446 participants had been vaccinated as adolescents before joining Italy's air force.
Ten years after vaccination, nearly two-thirds of the kids and almost nine out of 10 Italian air force recruits still showed immunity against hepatitis B.
"Unless accumulating data show a significant increase in hepatitis B virus infection in adolescents or adults who were vaccinated as children, a policy of booster vaccination in a population should not be recommended," they write.
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