Administered before girls start having sex, vaccines against the human papillomavirus — HPV — offer their greatest protection against infections that can lead to cervical cancer. Since the vaccination can only prevent infection, the benefits after the start of sex — to individual girls and women, as well as to public health — diminish in proportion to how much the odds increase that the person being vaccinated already has gotten HPV.
Now, a National Institutes of Health study has quantified potential benefits for vaccination among HIV-postive young women — women who are already having sex, but who, with HIV-damaged immune systems, also would be most endangered by a cancer-causing infection. The study found that while three-quarters of the women, aged 16 to 23, did have some type of HPV infection, nearly half of the women were not infected with either of the two types of the virus that cause most cervical cancer, and showed no sign of having been exposed yet to them.
The good news of the findings was that these HIV-positive young women and others like them, for whom cervical cancer would be especially life-threatening, could still be protected from getting a cancer-causing virus. It means that more physicians are likely to recommend the vaccine for girls already having sex, because the vaccine can still do what it is intended to do — prevent them from acquiring the most dangerous forms of HPV.
The sad part of the findings is that they are unlikely to benefit the young girls and women most threatened by cervical cancer — those in low and middle income countries, where HIV is endemic, but where the cost of the vaccine limits its use. Here, the three-dose vaccine costs as much as $350 to $400. In countries with more limited resources, HPV vaccines are often donated or made available at steeply discounted prices, but even then, their use is necessarily restricted for maximum public health benefit.
The data from the recent study do support World Health Organization recommendations that girls who have acquired HIV be vaccinated against HPV, but no lower and middle countries recommend vaccinating girls over the age of 15, study author Dr. Jessica Kahn, of Cincinnati Children’s Hospital Medical Center and the University of Cincinnati College of Medicine told Science Speaks. That effectively limits the good news in the study from spreading to countries where HIV — which exacerbates the odds of woman getting infected with HPV, of the HPV causing cancer, of the cancer being difficult to treat and likely to recur — helps make cervical cancer the number one cancer killer of women.
If the vaccination were highly affordable and readily accessible worldwide, the data would support giving “catch-up” vaccines to more young women who could benefit from it, Kahn said.
In the meantime, while the public health cost of distributing an expensive commodity inefficiently has been considered, not many studies that Kahn knows of have tallied the societal costs of cervical cancer’s toll in low-income countries — where it takes women with children to raise and work to contribute, in their most productive years.
“When they die,” she said, “the impact on society is tremendous. It is inestimable.”