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Everyone nowadays is aware that the Gardasil vaccine administered widely to young girls can protect against four strains of the human papillomavirus, a sexually-transmitted disease which can lead to cervical cancer. But what about older women? A new study argues the vaccine is indeed effective in protecting women ages 24 to 45 from HPV.

About 3 out of 4 sexually active women get HPV at some point in their lives. Though there are more than 100 HPV strains , most are harmless and disappear on their own without treatment. Gardasil protects against four of the strains of the virus that, when untreated, do bear serious medical risks: two which cause genital warts (strains 6 and 11) and two which can lead to cervical cancer (strains 16 and 18). Gardasil is only approved for girls ages 9 to 24, but a rising population of older women (24 to 45) are at risk of HPV infection. This is because more and more women are reentering the dating scene in middle age after a period of monogamy, such as after a divorce.

The ongoing multicenter, parallel, randomized, controlled, double-blind study tested the immunogenicity, safety, and efficacy of the quadrivalent HPV vaccine in 3819 Colombian women ages 24 to 45, none of whom had a history of genital warts or cervical disease. 1911 women received the vaccine, and the other 1908 were given a placebo. The researchers found that among the per protocol population (3222 women), the vaccine had a 90.5% efficacy rate against all strains of the virus. There were only 4 instances of infection in the vaccine group compared with 41 in the control group. The vaccine had an 83.1% efficacy rate against the two most common strains (HPV 16 and 18). Only four cases appeared in the vaccine group versus 23 in the control group. Researchers also looked at the intention-to-treat population, which included women who had not received all 3 installments of the vaccine or who did have a pre-existing HPV infection. When these subjects were included in the calculations, vaccine efficacy against all 4 types of HPV was 31%; against strains 16 and 18 was 24%. Because Gardasil will not protect women who were infected by HPV before they received the vaccine, the lower efficacy in the above mixed population suggests the “public health effect of vaccinating women ages 25 to 45 will be smaller than that recorded after vaccinating susceptible adolescents,” said researchers. Therefore, the maximum effect of vaccinating older women will be seen only in those who were susceptible to infection (engaging actively with new sex partners) and had not been previously exposed to HPV. However, most of the women in the study who were or had been HPV-positive were positive to only one strain of the virus. This means that the quadrivalent HPV vaccine could still be beneficial in protecting older women against the HPV strains they had NOT been infected with.

Though these findings are encouraging, some scientists are not as optimistic that the Gardasil vaccine will be effective in the older female population. They claim the new study is simply too small and that the vaccine’s true efficacy in the study group won’t be seen for several more years; the study has only followed the women for about 2.2 years.

Even if longer-term and larger-scale studies confirm the efficacy of the vaccine for older women, the problem for many women who believe they could be at risk of HPV infection is that the vaccine is currently only approved for girls 9 to 24. This means that right now insurers will not cover vaccination for older women until the shots are proven effective and approved for the older population. The fact that the vaccine’s three shots cost about $375 (not counting fees the doctor may charge for the visits) means that though these study results are encouraging, few older women will pursue vaccination until insurance companies begin covering it for them.

Regardless of whether women at any age receive the Gardasil vaccine, all women should still receive routine Pap smears, which check for cancerous or precancerous changes in cervix cells. Pap smears are almost always covered by private insurance as part of a woman’s routine gynecological exams.

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