The Advisory Committee on Immunization Practices (ACIP) and the CDC recently recommended that young adolescents receive two doses of HPV vaccine six months apart instead of the previous three doses. Teens and young adults who start the series later, at ages 15 through 26 years, will continue to need three doses of HPV vaccine to protect against cancer-causing HPV infections.
This recommendation was made after a review of data from clinical trials showed that two doses of HPV vaccine in younger adolescents (aged 9-14 years) produced an immune response similar or higher than the immune response in young adults (aged 16-26 years) who received three doses.
We recommend that the first dose of HPV vaccine be administered at age 11 or 12 years, but it could be given as young as age 9 and or at ages 13-14 years. The second HPV dose would be then be given 6 to 12 months after the first dose. However, if your adolescent does not receive the first dose of HPV vaccine until after their 15th birthday, that individual should receive three doses of HPV vaccine over a 6-month period.
This simplified schedule makes it easier for parents be certain that their adolescents are be protected from genital warts and cancers caused by Human Papilloma Virus (HPV) – the most common sexually transmitted infection in the United States.
CDC recommends only two HPV shots for younger adolescents:
https://www.cdc.gov/media/releases/2016/p1020-hpv-shots.html
HPV Infection Fact Sheet:
https://www.cdc.gov/std/hpv/stdfact-hpv.htm