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Additional Vaccine-Covered HPV Genotypes
Found Yearly in Older HIV+/HIV- Gay Men
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7th IAS Conference on HIV Pathogenesis, Treatment and Prevention, June 30-July 3, 2013, Kuala Lumpur
Mark Mascolini
Every year 1 in 5 middle-aged or older gay men in an Australian cohort became infected with a human papillomavirus (HPV) genotype covered by the currently available quadrivalent HPV vaccine in a large prospective study [1]. Every year more than 1 in 4 men became infected with an HPV genotype covered by the experimental nonavalent HPV vaccine in this 3-year study of men with and without HIV infection. The findings suggest middle-aged and older gay men--not just young men--can benefit from HPV vaccination.
A high proportion of gay men are infected with HPV types that can cause anal cancer or genital warts. Bivalent and quadrivalent vaccines are available to protect children and adults from HPV infection, and a nonavalent vaccine (active against 9 HPV types) is being studied. But guidelines recommend HPV vaccination only for boys or girls or younger men or women, apparently because they assume older people already carry HPV types covered by the vaccines. Researchers working with the Study for the Prevention of Anal Cancer (SPANC) conducted this analysis of HIV-positive and negative gay men to determine prevalence and incidence of HPV types covered by the quadrivalent and nonavalent vaccines.
SPANC is a community-recruited prospective study of the natural history of anal HPV and anal cellular abnormalities in HIV-positive and negative gay men at least 35 years old. At five study visits (baseline and 6, 12, 24, and 36 months), participants complete detailed behavioral questionnaires and undergo anal examination. Liquid-based anal cytology is followed by high-resolution anoscopy, and visible abnormalities trigger biopsy for histologic assessment.
The investigators also assess cytologic media for HPV genotypes. The quadrivalent vaccine covers types 6, 11, 16, and 18, and the nonavalent vaccine covers those four types plus 31, 33, 45, 52, and 58. The investigators defined prevalent infection as detection of one or more vaccine-preventable genotypes at the baseline visit. They defined incident infection as detection of one or more vaccine-preventable genotypes after a negative result for that genotype.
This analysis focused on 342 men enrolled in SPANC between September 2010 and March 2013. Ninety-eight men (28.7%) had HIV infection, and median age stood at 49 years and ranged from 35 to 79. Among HIV-positive men, 88.8% were taking antiretroviral therapy and 83.7% had an undetectable viral load. Most HIV-positive men (83.2%) had a recent CD4 count above 350. HPV genotyping results were available for 318 men.
At the baseline visit, half (51.3%) of SPANC participants had at least one HPV type covered by the quadrivalent vaccine and almost two thirds (64.5%) had an HPV type covered by the nonavalent vaccine. HPV-16, which can lead to anal cancer, was the most prevalent HPV type, found in almost one third of men (30.2%). The next most prevalent types were HPV-6 (in 20.4%) and HPV-52 (in 15.2%).
During each year of follow-up, 1 in 5 men (20.2 per 100 person-years) picked up at least one HPV type covered by the quadrivalent vaccine, and more than 1 in 4 (27.3 per 100 person-years) picked up at least one HPV type covered by the nonavalent vaccine. HPV-6, which can lead to anal warts, was the most frequently detected new HPV type (9.2 per 100 person-years), followed by HPV-45 (7.9 per 100 person-years) and HPV-16 (5.3 per 100 person-years).
Compared with HIV-negative men, those with HIV had almost 90% higher odds of having a nonavalent genotype at the baseline visit (odds ratio [OR] 1.89, P = 0.002). HIV-positive men had 80% higher odds of acquiring a new nonavalent genotype during follow-up (OR 1.8, P = 0.033). There were trends toward higher quadrivalent or nonavalent genotype prevalence in younger men (P = 0.08 and P = 0.058). But age had no impact on rates of new infection with the HPV genotypes studied.
Results showing a substantial number of new vaccine-covered HPV types acquired yearly suggested to the investigators "that prophylactic quadrivalent or nonavalent vaccination of older homosexual men would prevent future HPV-associated disease." In Australia the quadrivalent vaccine is recommended for men up to age 26, as it is in the United States [2].
References
1. Poynten IM, Tabrizi S, Jin F, et al. Potential impact of human papillomavirus (HPV) vaccination among HIV-positive and HIV-negative homosexual men: vaccine-preventable anal HPV types in the SPANC study. 7th IAS Conference on HIV Pathogenesis, Treatment and Prevention, June 30-July 3, 2013, Kuala Lumpur. Abstract WEPE536.
2. Centers for Disease Control and Prevention. Human papillomavirus (HPV). HPV vaccines. http://www.cdc.gov/hpv/vaccine.html
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