Does vaccinating one sexual partner benefit the other?
A new study by McGill University will examine whether vaccinating only one partner in a couple against the human papillomavirus (HPV) can help prevent transmission of HPV to the unvaccinated partner.
The study – called TRAP-HPV, an acronym for Transmission Reduction And Prevention with HPV vaccination – is a randomized placebo-controlled double-blind trial involving 500 sexually active couples. The study aims to determine the efficacy of an HPV vaccine in reducing transmission of genital, anal, and oral HPV infection in unvaccinated sexual partners of vaccinated individuals.
HPV is the leading cause of cervical cancer, the second most common cancer in women globally. Prophylactic vaccines against certain high-risk HPV types have been shown to be effective in preventing infection. However, much remains to be understood on the effects of HPV vaccine on the blockage of transmission of target HPV types to sexual partners of vaccinated individuals.
“This is the first study to look at whether unvaccinated partners of vaccinated individuals have a benefit in terms of protection from HPV infection,” explained Eduardo Franco, Director of the Division of Cancer Epidemiology and leader of the study. “It will help us understand the important issue of herd immunity from HPV vaccination. If partner protection is sufficiently high we may be able to get adequate population level immunity from much less than 100% vaccination coverage and devote our scarce public health funds to other pressing needs.”
“Efficacy studies of the HPV vaccines generally look at genital HPV infections, but our study will also be looking at other anatomical sites that HPV infects, such as the anal and oral regions,” says Kristina Dahlstrom, postdoctoral fellow, Department of Oncology, Division of Cancer Epidemiology. “Increasing the knowledge about HPV transmission dynamics will benefit cost-effectiveness studies and have implications for decision-making when implementing population-level vaccination strategies”.
The U.S. Centers for Disease Control considers HPV the most common sexually transmitted disease in the world. Another McGill study called HITCH (HPV Infection and Transmission in Couples through Heterosexual activity), also from Dr. Franco’s team, found more than half (56 per cent) of young adults in a new sexual relationship were infected with HPV. Of those, nearly half (44 per cent) were infected with an HPV type that causes cancer. HPV is transmitted through sexual contact and persistent infections by specific types of HPV can cause cancer. Researchers at the International Agency for Research on Cancer estimate that HPV was responsible for 610,000 cases of cancer worldwide in 2008, about 5% of the world’s cancer burden. Most of these are cervical cancer, but HPV is also an important cause of cancers of the head and neck, anus, penis, vulva, and vagina. The World Health Organization (WHO) estimates that more than a half million women are diagnosed with cervical cancer annually and that the majority die from the disease – making it the 2nd most frequent cancer among women worldwide. It is also estimated that 20-30 per cent of head/neck cancers are associated with HPV, with growing evidence linking these to the practice of oral sex. Since HPV-associated head and neck cancers are more likely to occur in men, protection of both genders through vaccination is important.
The TRAP-HPV study will recruit 500 sexually active couples in Montreal. The treatment will be vaccination with Gardasil (Merck), the HPV vaccine, and the placebo will be vaccination with Havrix (GSK), a vaccine against hepatitis A. Those vaccinated with Havrix will still be susceptible to HPV infection. A couple can be randomized to both receive Gardasil, one receives Gardasil and the other Havrix, or both receive Havrix (the control group). Couples will be followed for one year with clinic visits to collect genital, anal, and oral samples to determine their HPV infection status. They will also provide information about their demographics and sexual behaviors. Those who wish to participate in the study should contact Ms. Allita Rodrigues at traphpv [at] mcgill [dot] ca for more information.
The study is funded primarily by the Canadian Institutes of Health Research and has also been supported by Merck, which provided free HPV vaccines and an unconditional grant to McGill.
For more information on the study, please visit: http://www.mcgill.ca/traphpv/