Good news for young adults: The CDC recommends only two doses of the human papillomavirus (HPV) vaccine instead of the previously recommended three-shot regimen. Recent studies have shown if the first shot is administered before age 15, two shots confer immunity. If the series begins after age 15, the CDC still recommends three shots over a six-month period. For the two-shot regimen, the second shot should be administered six to 12 months after the first dose. The HPV vaccine prevents cervical, vaginal, anal, and head and neck cancers, as well as precancerous lesions and genital warts.