Harvard Women's Health Watch

New cervical cancer vaccine highly promising, but questions remain

Many experts recommend vaccinating all preteen girls. Others urge caution.

In 2006, the FDA approved Gardasil, the first vaccine designed to prevent infection with the human papillomavirus (HPV). There are more than 100 strains of HPV, and 30 to 40 are sexually transmitted. Gardasil, made by the drug company Merck, targets strains 16 and 18, which are implicated in 70% of cervical cancers, and strains 6 and 11, which cause 90% of genital warts. The vaccine was approved on the basis of early results showing that it was virtually 100% effective in preventing infection by the targeted strains for up to 18 months.

Given as a series of three shots over six months, Gardasil is licensed for use in girls and young women, ages 9 to 26. It works best if it's given before the start of sexual activity and potential exposure to HPV. Since its approval, the Advisory Committee on Immunization Practices — an arm of the Centers for Disease Control and Prevention (CDC) — has recommended routine vaccination of 11- and 12-year-old girls (and girls as young as age 9, at their clinicians' discretion). The CDC also recommends that Gardasil be offered to older girls and young women on the assumption that even if they've been exposed to HPV, they may not have encountered the particular strains contained in the vaccine.

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