Study shows no link between HPV vaccine and increased sexual activity

Big news on the sexual health front: a new longitudinal study was published yesterday in JAMA showing that young women who have received the HPV vaccine are no more likely to contract other STIs than unvaccinated women. While it is never a good idea to make generalizations about anything based on one study, this particular one seems well-designed and will hopefully lead to further study on this question. 'The Public Vaccinator' by Lance Calkin. Credit: Wellcome Library, London.

HPV causes cervical, vaginal, and anal cancer and has been connected to various head and neck carcinomas. The vaccine protects against four strains of the virus most often responsible for those cancers. To be clear: the HPV vaccine is a vaccine against cancer. Despite the potential benefits, many parents (and non-parents) fear that by giving their child the HPV vaccine, their child will feel free to engage in risky sexual behavior.

Because of this fear, HPV vaccine uptake has been abysmal in the United States. Only about half of young women and one-third of young men have received the first dose of the HPV, and even fewer have completed the three-dose series.

Looking at a sample group of women over 208,000 women aged 12-18, researchers found that young women recieved the HPV vaccine were no more likely to seek treatment for chlamydia, gonorrhea, herpes, HIV/AIDS, or syphilis than were unvaccinated women. That’s right, there was no evidence that getting the HPV vaccine increased the likelihood of being diagnosed with an STI.

Using pharmacy claims, researchers also determined that vaccinated women were more likely to use oral contraceptives. 17.9% of vaccinated women across age ranges received a prescription for hormonal birth control while 9.2% of unvaccinated women did. This could be due to a few factors: young women who intended to engage in any sexual activity were more likely to request the vaccine as well as contraceptives; the HPV vaccine was suggested by doctor during appointments for acquiring contraceptives; or parent perception of daughters’ likehood of being sexually active influenced their decision to vaccinate or seek contraceptives for their child.

There are, of course, some limitations to this study. The researchers were only able to access records, so by design they missed undiagnosed STIs, may have included STI screenings rather than diagnoses, and omits the use of non-prescription contraceptives like condoms. Researchers were also unable to use records from anonymous clinics. Researchers also could not acquire information about SES and motivations for receiving the vaccine. This study also does not look at young men in the same age range, which would give a more complete picture of how HPV vaccine impacts adolescent sexual activity.

The psychology of vaccine risk perception is fascinating. Beyond the concerns of “naturalness,” parents who are less inclined to vaccinate may feel more responsible for potential injury to their child if the injury is connected to a vaccine rather than to a disease that could have been prevented by that vaccine. A parent whose child has a seizure after the HPV vaccine may feel more responsible for that event than if the child contracts HPV. I wonder how the parents would feel if, after a decade, their child is diagnosed with an HPV-related cancer.

To an extent, I get it. I’m not a parent, but I do possess empathy and can imagine how frightening parenting must be. The world seems full of danger, and parents want to do everything in their power to keep their children safe. Sometimes not acting--not vaccinating--seems safer than risking the side effects of the vaccination or of the disease itself.

Fearing risky adolescent sexual activity also makes some sense to me. Most parents don’t want to see their child become a parent during their sophomore year of high school. Most parents don’t want their child to live with HIV or herpes.

But nearly everyone becomes sexually active at some point in their lives, and about 70% of people have their first sexual experience before age 19.  Half of sexually active men and women will have HPV. That means that means that when parents decide not to vaccinate their children, they allow their children to have a one-in-two chance of contracting HPV. And while most cases of HPV clear up on their own with no adverse effects, there are more than 33,000 cases of HPV-related cancer diagnosed each year in the United States.

No study can stand alone. We should not take the results of this study and make bold proclamations about young women’s behavior and sexual activity. I do believe, however, that this robust study provides some much-needed evidence that reducing young women’s risk of infection does not turn them into crazed sex machines making risky choices. I look forward to subsequent studies that can provide more evidence for parents to use to make informed choices.

Note: I know that women over age 18 don’t need parental permission in order to get the vaccine and may be more inclined to seek it out. But this study looked only at women under age 18, so I stuck to that age group as well.