Research sheds light on HPV transmission

If your clinical practice includes care of college-age youth, you will want to review the results of a new study of university students. Why? Its findings indicate that more than half of young adults in a new sexual relationship were infected with human papillomavirus (HPV).1 Among those infected, nearly half (44%) of infections were from an HPV type that causes cancer, the scientists report.1

Researchers at the McGill University, its Cancer Epidemiology Unit, and the Université de Montréal/Centre Hospitalier de l'Université de Montréal, all in Montréal, Canada, conducted the HITCH (HPV Infection and Transmission in Couples through Heterosexual Activity) Cohort Study to determine the prevalence of HPV infections among 263 recently formed couples. The scientists believe this is the first large-scale study of HPV infection among couples early in their sexual relationships when transmission is most likely.

Participants in the study are young women attending university or junior college in Montreal, Quebec, and their male partners, with new couples defined as those who have been together for six months or less. Study participants fill out questionnaires regarding their sexual history and provide genital specimens for laboratory testing for the presence of 36 HPV genotypes. Recruitment for the study is continuing.

Current study results indicate there is a high probability of HPV transmission between partners. Researchers found 583 type-specific HPV infections among 169 couples for whom at least one partner was infected. Of these, 42% were of the same type for both partners. Results suggest that the presence of HPV in one partner was the strongest predictor of finding the same HPV type in the other partner.1

How might clinicians in reproductive health settings include the findings of this recent paper in their clinical practice when it comes to care of young adults? "In our HITCH study, more than half — 56% — of all participants were infected with at least one HPV type, almost half — 44% — were infected with an HPV type that causes cancer, and our results suggest that HPV is an easy virus to get and transmit," says Ann Burchell, PhD, the project coordinator and a postdoctoral fellow at the Cancer Epidemiology Unit. "For me, the take-home message is that all young people should expect that they will be exposed to HPV."

Getting the HPV vaccine and employing safer sex practices, such as using condoms, will help to reduce young adults' chances of getting infected, says Burchell. "Most importantly, we should educate all women about the importance of cervical cancer screening throughout adulthood and emphasize that you don't need to have had many partners to be at risk," Burchell says.

Screening programs key

How do the findings of the current study underscore the importance of prevention programs for HPV-associated diseases such as cervical cancer screening and HPV vaccination?

The HITCH study examines early events related to the natural history of HPV infection, observes study leader Eduardo Franco, DrPH, professor of epidemiology and oncology director in the Division of Cancer Epidemiology at McGill University. The fact that researchers found such high rates of HPV infection in young couples underscores how common the virus is and how inconsequential these infections are at this young age, he states. The vast majority of HPV infections will be effectively cleared by the immune system by the time young adults reach age 25 or 30. However, the concern exists for a few women whose infections with the high-risk types of HPV become persistent, Franco notes. These women might develop cervical precancerous abnormalities, which if left undetected and untreated, might progress to cervical cancer, he states.

Screening with the Pap test permits detecting these abnormalities, which prompts treatment and eventually eradicates the lesions, says Franco. Testing for HPV, using clinically validated assays, might in the future replace or serve as an adjunct to Pap test screening, notes Franco. This testing might improve the efficiency and accuracy of cervical cancer screening in the future. In developing countries, HPV testing also might help improve coverage, while requiring less stringent quality assurance than Pap cytology in screening programs, states Franco.

Put prevention first

The effectiveness of screening notwithstanding, preventing HPV infection from happening in the first place is a more attractive goal, says Franco. HPV vaccination prior to first sexual exposure, as has been recommended, has been proven effective in reducing risk of infections with the two main genotypes that can cause cervical cancer, HPV 16 and 18, and in the case of the quadrivalent vaccine, two types that cause genital warts, HPV 6 and 11.2 These four types of HPV are relatively common and represent a substantial proportion of the infections in the HITCH study, observes Franco.

Screening will have to continue, says Franco. Although the available vaccines can prevent up to 75% of cervical cancers, women who have been vaccinated still can develop infections with high-risk HPV types other than those present in the vaccines, he states. "There is much ongoing research that is attempting to find the most cost-effective strategies for screening in the post-HPV vaccination era," says Franco. "Our group is also conducting research in this area, exploring the most promising technologies and their combinations."

Consistent condom use also is important in disease prevention. Previous research indicates that consistent condom use offers protection against high-risk and low-risk types of HPV.3

Researchers in the current report that frequent condom use was protective in men, particularly if his partner was HPV-infected [odds ratio (OR) = 0.64, 95% confidence interval (CI): 0.50-0.82]. This effect was less so among women with an infected partner (OR = 0.88, 95% CI: 0.69-1.11).1

References

  1. Burchell AN, Tellier PP, Hanley J, et al. Influence of partner's infection status on prevalent human papillomavirus among persons with a new sex partner. Sex Transm Dis 2010; 37:34-40.
  2. Muñoz N, Kjaer SK, Sigurdsson K, et al. Impact of human papillomavirus (HPV)-6/11/16/18 vaccine on all HPV-associated genital diseases in young women. J Natl Cancer Inst 2010; Feb 5. [Epub ahead of print.]
  3. Winer RL, Hughes JP, Feng Q, et al. Condom use and the risk of genital human papillomavirus infection in young women. N Engl J Med 2006; 354:2,645-2,654.