Children's Vaccines Health Center

Vaccine FAQ

10. Why are some vaccines given a few times in childhood, and others given every year?

"Before a vaccine is licensed, it is tested to understand how well it can protect," says Schuchat. "Some vaccines need multiple doses to provide protection, and some need boosters five or 10 years later to make sure the protection stays active. Some vaccines given in childhood wear off as a child becomes a teen, so a new vaccination is needed.

"The vaccine that has to be given every year is the flu vaccine. That has to be given every year because the flu viruses change quickly. So a totally new vaccine is made each year."