"Universal vaccination in infancy provides long-term protection," Dr. Yen-Hsuan Ni, the study's lead author from the National Taiwan University in Taipei, wrote in an e-mail.

Taiwan mandated hepatitis B virus (HBV) immunization for all infants in 1984, in response to extremely high rates of infection. Hepatitis B infection is a prime cause of liver cancer, the second most common cancer type in Taiwan.

In 2009, study participants younger than age 25 were far less likely to be infected than those between the ages of 26 and 30 -- who were born before universal vaccination, the researchers found.

"It's efficacy in young adults is clear," Ni told Reuters Health, explaining that medical experts had questions about how long the vaccine's protective effect would last. Booster shots, which are generally not recommended for hepatitis B, were not given to subjects in the study.

The findings reinforce five previous surveys -- done at five-yearly intervals since 1984 -- which also found lower infections among those born after the mandate.

Under the Taiwanese program, infants born to infected mothers also get a shot of a protein to fight against the virus known as an antibody within 24 hours of birth, but this did not completely eliminate the spread of the virus from mother to child, the study noted.

"Mother-to-infant transmission remains the key route of vaccine failure that needs to be overcome," Ni said.

The study, published in the Journal of Hepatology, suggests that other countries may benefit from including compulsory hepatitis B vaccination for infants.

Hepatitis B is a viral infection that attacks the liver. The virus is spread by contact with the blood or other bodily fluids of an infected person.

An estimated 350 million people worldwide have the hepatitis B virus. Almost 100,000 new people are infected each year in the United States, according to the non-profit Hepatitis B Foundation.

The World Health Organization recommends hepatitis B shots for all babies. The three-part vaccine series usually costs $75 to $165, and is available often free of charge from health clinics. Common side effects include soreness, swelling and redness where the shot is injected.

BOOSTER SHOTS UNNECESSARY

For the new study, funded by the National Taiwan University Hospital, Ni and his colleagues enrolled more than 3,300 participants under 30. Of these subjects, more than 2,900 -- born after the mandate -- received at least three doses of vaccine in their first year. Approximately 370 subjects, born before 1984, were not universally vaccinated.

When they collected blood samples from January to December 2009, Ni's team found that less than one percent of the universally vaccinated group carried the virus and were infectious to others, compared with 10 percent of those who weren't universally vaccinated.

Among subjects over age 20, the infection rate did not increase significantly from 1989 to 2009, making universal booster doses unnecessary, the study noted.

Fifty-six percent of those born after universal vaccination developed immunity to the disease, versus 24 percent in the group born before it began. Seven percent of the group that was universally vaccinated had an infection in their history but possibly had recovered, compared with 28 percent of the group that was not.

Most cases of vaccine failure were related to the mother's status, the study found. Of the 25 subjects who developed an infection despite getting immunized, 86 percent had mothers who carried the virus.

Globally, gaps in treatment -- including spread of the virus from mother to baby -- need to be plugged to eliminate hepatitis B, said Dr. Solomon Chen, a visiting fellow in global health at the Harvard School of Public Health.

"The issue of vaccine failure due to intrauterine transmission should be overcome," Chen, who was not involved in this study but studied under its authors in Taiwan, told Reuters Health.

SOURCE: bit.ly/NU4fKa Journal of Hepatology, online June 4, 2012.

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