Virginia students entering sixth grade in the fall must have a hepatitis B vaccination this summer, or they won’t be allowed in school.

The requirement is part of a two-pronged attack on the virus mandated when the General Assembly approved immunization guidelines in 1999. All students born in 1994 and after are required to have the hepatitis B vaccination before entering school.

The provision that affects the sixth-graders is intended to protect older students not vaccinated earlier, said Jim Farrell, director of the Division of Immunizations of the Virginia Department of Health.

County health departments give the vaccinations free to children in those two groups.

Hepatitis B is part of a series of viruses that affect the liver. It is spread by blood and body fluids and is much more contagious than the virus that causes AIDS, Farrell said. Though not always fatal, the disease can lead to liver scarring, liver cancer, and lifelong infection, according to the U.S. Centers for Disease Control and Prevention.

Children, though not generally a high-risk group for the disease, will be protected by the vaccine as they get older, Farrell said.

“You never know when someone is going to have a risk factor,” Farrell said. “At middle school, that is the age when people are entering the high-risk years.”

Full immunization takes two or three doses, depending on the vaccine used, and requires several months between shots. Students can start sixth grade in the fall if they show they have taken at least one shot and are on schedule to receive the remaining doses.