It is recommended that 11-to-12-year-olds receive 2 doses of HPV vaccine at least 6 months apart to protect against cancers caused by HPV infections. Teens and young adults who start the series later, at ages 15 through 26 years, will need 3 doses. Clinical trials showing 2 doses of HPV vaccine in younger adolescent (aged 9-14 years) produced an immune response similar or higher than the response in young adults (aged 16-26 years) who received 3 doses.