Washington: Anti-hepatitis A virus (HAV) shots give infants immunity for least 10 years, according to latest research.
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 Organisation estimates that 1.4 million cases of HAV occur worldwide every year.
HAV affects the liver and typically occurs in areas with poor sanitation where ingestion of contaminated food or water can transmit the virus, the journal Hepatology reports.
Early symptoms include fatigue, fever, abdominal pain, nausea, appetite loss, jaundice, a yellowing of the skin or whites of the eyes, dark urine, through which bile is excreted from the blood stream.
In the United States, HAV cases have decreased by 90 percent in the past 20 years, with roughly 20,000 new cases reported each year, thanks to routine vaccination, according to a statement of the Centres for Disease Control and Prevention (CDC).
Umid Sharapov, a CDC epidemiologist, who led the study, said this was the first study to examine the effectiveness of a two-dose inactivated hepatitis A vaccine in children younger than two years over a 10-year period.
Researchers also investigated whether maternal anti-HAV antibody transfer to children impacts the vaccine protection against HAV. With parental consent, they enrolled full-term healthy infants at six months. Mothers were tested for total antibody to HAV.
The 197 infants and toddlers were broken into three age groups: group one - infants aged between six and 12 months; group two - toddlers between 12 and 18 months; and group three -toddlers between 15 and 21 months.
Each group was randomised 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 10 years after the second dose of hepatitis A vaccine.
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 10-year follow-up, most children retained anti-HAV protection.