News flash--condoms do help prevent HPV

Especially in religious circles, much has been made about the "uselessness" of condoms for the prevention of infection with the human papilloma virus (HPV). This is the virus that is responsible for almost all cases of cervical cancer, against which a new vaccine was recently approved (for more background, see this post). Approximately 20 million Americans are currently infected with HPV, and over their lifetime, about half of sexually active adults will be infected at one point. Though most strains of the virus are harmless, a small portion of them cause cervical cancer in women, a disease that affects over 10,000 women every year (with a ~40% mortality rate).

These numbers, and the previous uncertainty about the level of protection condoms provide against HPV infection, has led to wild claims and fear-mongering by some. For example, an article by the Family Research Council ("Defending faith, family, and freedom") states the following (after extensive quote-mining) regarding condoms and HPV:

Despite the evidence, people and organizations supposedly dedicated to public health are pushing condom use as an effective deterrent to the spread of STDs, including HPV. They fail to adequately communicate that condoms do not work against HPV; nor do they promote abstinence until marriage as the only way to stop this potentially deadly disease.

and later

We can no longer ignore the HPV epidemic. With knowledge of the prevalence of HPV, its link to cervical cancer and condoms' inability to protect against the transmission of this disease, the following proposals should be implemented:

1. Congress should require the CDC to conduct studies on the nature and effects of HPV. The CDC should also be required, as it is with other STDs, to report on HPV transmission rates.

2. Condom manufacturers should be required to include a warning on their packages that alert people to condoms' ineffectiveness in shielding against HPV transmission.

3. A public health campaign, organized by the CDC, should be launched to heighten public awareness of HPV and to shatter the myth that condoms provide protection against the disease.

A new NEJM paper, however, shows that condoms do, indeed, provide protection against HPV.

The authors performed a longitudinal study (identifying participants--women who were either virgins or who had recently had sexual intercourse for the first time--and following them over time) in order to determine HPV status and sexual behavior (including condom use). Of the subjects who completed the study (and over 120 were excluded, mostly because they'd had sex more than 2 weeks prior to enrollment, or because they reported having no vaginal intercourse), the numbers were good:

The mean (±SD) age of the 82 subjects at enrollment was 19.3±0.7 years. The subjects completed 709 visits. The mean follow-up time was 33.9±11.8 months, the mean number of visits per woman was 8.6±2.9, and the median time between visits was 4.1 months. Diary data were 90.7 percent complete, and condom data were recorded on 99.3 percent of days that intercourse was reported.

So, on average, the subjects were followed for almost 3 years, returned for 8 follow-up visits (which included an interview with a nurse, pelvic exam and swab for HPV isolation), and did a good job of keeping up on their web diaries charting their sexual activity. As far as the results, they found that women whose partners consistently used condoms had a much lower risk of acquiring HPV than those whose partners infrequently used condoms, and this held for both high-risk and low-risk types of HPV. In addition, these women experienced fewer cervical lesions than those whose partners infrequently used condoms. They summarize in their abstract:

The incidence of genital HPV infection was 37.8 per 100 patient-years at risk among women whose partners used condoms for all instances of intercourse during the eight months before testing, as compared with 89.3 per 100 patient-years at risk in women whose partners used condoms less than 5 percent of the time (adjusted hazard ratio, 0.3; 95 percent confidence interval, 0.1 to 0.6, adjusted for the number of new partners and the number of previous partners of the male partner). Similar associations were observed when the analysis was restricted to high-risk and low-risk types of HPV and HPV types 6, 11, 16, and 18. In women reporting 100 percent condom use by their partners, no cervical squamous intraepithelial lesions were detected in 32 patient-years at risk, whereas 14 incident lesions were detected during 97 patient-years at risk among women whose partners did not use condoms or used them less consistently.

This study certainly isn't perfect. The 82 subjects in their final pool is still a relatively small number, and as college students, these results aren't necessarily generalizable to the population at large. Additionally, as with all STD studies, condom use and sexual behavior is self-reported, inviting misclassification bias and errors that may skew the results. (For instance, were all those girls really virgins, and thus, the HPV infections really incident and not previously present? Did they actually use condoms as reported? Did they under-report their frequency of new partners? etc.) However, the authors suggest, based on their use of both in-person interviews and online diary reporting, that the online method serves to lessen some of the stigma and result in more truthful answers.

Finally, it should be noted that there still were infections even in those who reported faithful condom use. This was expected given previous research (and the fact that HPV can be transmitted via skin-to-skin contact, in addition to fluids), but it still doesn't jibe with characterizations (like that I quoted above) that condoms are "worthless" at preventing HPV infections. No one has said, ever, that condoms are 100% effective at preventing anything, be it sexually-transmitted infections or pregnancy. But to pose the false dichotomy--either perfect or worthless--is a huge detriment to those women who can be (and are) protected by consistent use of condoms. No one is denying that abstinence is the best policy if you want to steer clear of STDs, but for many, it is simply unrealistic; and even in a committed, monogamous relationship, if one partner is infected due to a previous sexual partner, faithfulness ain't gonna help you. Condoms will, and this new paper shows the extent to which they can prevent even HPV infections.

Reference

Winer et al. 2006. Condom Use and the Risk of Genital Human Papillomavirus Infection in Young Women. NEJM. 354:2645-2654. Link and NEJM perspective.

Image from http://www.inca.gov.br/cancer/imagens/hpv_fig1.jpg