For the last 10 years, hepatitis A vaccination in children two years of
age remains effective, finds recent study published in August issue of Hepatology. The study found that any transfer of the mother's HAV
antibodies does not lower the child's immune response to the vaccine.
The World Health Organization (WHO) estimates that 1.4 million cases
of HAV occur worldwide each year. HAV affects the liver and typically
occurs in areas with poor sanitation where ingestion of contaminated
food or water can transmit the virus. In the U.S., HAV cases have
decreased by 90% in the past 20 years, with roughly 20,000 new cases
reported each year according to the Centers for Disease Control and
Prevention (CDC). Experts attribute the decline in HAV cases in the U.S.
to routine vaccination of children 12 to 18 months.
According to lead author Dr. Umid Sharapov, an epidemiologist with
the CDC and his coauthors, this is the first study to examine the
effectiveness of a two-dose inactivated hepatitis A vaccine in children
younger than two years of age over a ten-year period. In addition, the
researchers investigated whether maternal anti-HAV antibody transfer to
their children impacts the vaccine protection against HAV.
With parental consent, researchers enrolled full-term infants who
were healthy at six-months of age. Mothers were tested for total
antibody to HAV. The 197 infants and toddlers were broken into three age
groups: group one-infants 6 to 12 months; group two-toddlers between 12
and 18 months; and group three-toddlers 15 to 21 months of age. Each
group was randomized by maternal anti-HAV status. HAV antibody levels
were measured at one and six months, and additional follow-up took place
at three, five, seven and ten years after the second dose of hepatitis A
At one month following the second dose of the hepatitis A vaccine
children in all groups showed signs of protection from the virus. At the
ten-year follow-up most children retained anti-HAV protection. In the
first group, 7% and 11% of children born to mother's without and with
antibodies to the HAV virus, did not retain HAV protection from
vaccination, respectively. Additionally, 4% of group three children born
to anti-HAV negative mothers lost HAV protection.
"Our study demonstrates that seropositivity to hepatitis A persists
for at least ten years after primary vaccination with two-dose
inactivated HAV vaccine when administered to children at ages 12 months
and older, regardless of their mothers' anti-HAV status," concludes Dr.
Sharapov. "These findings support current CDC/ACIP guidelines for
routine administration of two doses of inactivated hepatitis A vaccine
to all children in the U.S. beginning at the age of 12 months." The
authors point out that a future booster dose may be necessary to
maintain protection against HAV and they will continue follow-up
participants into their teens to monitor benefit of the initial