(RxWiki News) While some vaccines can be given once and offer protection for life, others require booster shots and still may wear off over time.
A recent study has found that the two-shot sequence of the hepatitis A vaccine, administered to children as infants or toddlers, offers them protection for at least ten years, even if they had already had some antibodies from their mothers.
"Follow the CDC's recommendations for your child's immunizations."
The study, led by Umid Sharapov, MD, an epidemiologist at the Centers for Disease Control in the Division of Viral Hepatitis, looked at how effective the hepatitis A vaccine is in children.
The researchers also wanted to find out whether a child might have a poorer response to the hepatitis A vaccine if the child received antibodies against hepatitis A from the mother.
The hepatitis A vaccine is an inactivated one - which means it is not made from the live hepatitis A virus - and is administered in two doses.
When a person receives a vaccine, it tricks the body into thinking that the disease is present, so the immune system creates antibodies to fight it.
These antibodies build up and remain in the body; if the person ever contracts the actual disease, the body fights it off before the infection can even begin.
The researchers were concerned that a child's body might not produce as many antibodies in response to the vaccine if the child already had some antibodies from their mother.
To explore how children's bodies responded to the vaccine at different ages and with and without their mothers' antibodies, the researchers recruited 197 6-month old babies, who were split into three groups.
One group received their first hepatitis A vaccine shot at age 6 months, followed by a booster shot at 12 months.
The second group received their first shot at 12 months and the booster at 18 months. The third group received the first shot at 15 months and the booster at 21 months.
Before any babies received the vaccine, their blood was tested to see if they already had hepatitis A antibodies from their mothers.
Then their levels of antibodies were tested again one month and six months after the booster shot, and then three years, five years, seven years and ten years after the booster shot.
All of the children had evidence of adequate antibodies for hepatitis A one month after the two shots, which meant that even the babies who had their mothers' antibodies still responded well to the vaccine.
At the 10-year mark, most of the children still had good protection from hepatitis A. In group one, 7 percent of the children who did not have antibodies from their mothers and 11 percent of the children who did have their mothers' antibodies did not have adequate protection from the virus.
In the third group, 4 percent of the children whose mothers did not pass along their antibodies no longer showed enough protection against hepatitis A. But the rest of the group three children who didn't have their mothers' antibodies had the highest rate of protection from the virus.
The researchers concluded that the data from this study supported the CDC's current recommended schedule for hepatitis A vaccination.
"Our study demonstrates that seropositivity to hepatitis A persists for at least ten years after primary vaccination with two-dose inactivated hepatitis A vaccine when administered to children at ages 12 months and older, regardless of their mothers' [hepatitis A antibody] status," the authors wrote.
"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," they wrote. ACIP is the Advisory Committee on Immunization Practices, the committee at the CDC that makes recommendations on immunization schedules.
Approximately 1.4 million cases of hepatitis A occur across the world every year, according to estimates from the World Health Organization.
In the U.S., however, cases of hepatitis A rates have decreased by 90 percent in the past two decades - with only about 20,000 new cases a year - thanks to routine vaccination of young children.
The study was published in the August issue of the journal Hepatology. The authors reported no conflicts of interest.