Although secondary prevention strategies such cytology and HPV testing have reduced the incidence of cervical cancer, there is no current consensus on strategies to reduce anal cancers in women. Primary prevention strategies such as HPV vaccination have the potential to reduce the incidence of all cancers related to HPV infection, including both cervical and anal cancers. In the US, there are 3 approved vaccines for the prevention of HPV, but Gardasil 9, which covers 7 high-risk strains of the virus along with 2 other strains, is the only vaccine currently available.
Erna M. Kojic, MD, Chief of Infectious Diseases, Mount Sinai St. Luke’s and Mount Sinai West in New York City, and a researcher in the area of HIV and HPV coinfection, set out to investigate the incidence, prevalence and clearance of the 7 high-risk strains of HPV covered by Gardasil 9 as well as the 7 high-risk strains not covered by the vaccine in women with HIV.
Kojic and colleagues enrolled 126 women from 7 clinics in 4 US cities in this prospective observational cohort study. The women included in the study were HIV positive, ethnically diverse, generally healthy, and currently receiving outpatient care. Cervical and anal tissue samples were collected at baseline and annually for cytology and HPV testing for a follow-up period of 5 years.
At baseline, “HPV infection was more prevalent at the anus (90%) than the cervix (83%).” The prevalence of the high-risk strains both covered and not covered by the Gardasil 9 vaccine was also higher at the anus than the cervix. Overall, the clearance of any strain of HPV was lower at the anus than the cervix. In addition, the clearance of any high-risk strain of HPV was also lower at the anus than the cervix.
The researchers observed that HPV infection cleared more slowly at the anus versus the cervix regardless of the strain of the virus. The differences in infection between anatomical compartments, speculated by the authors, was related to local mucosal environment, different sexual behaviors and transmission, or efficacy of the immune response to clear infection, although they also noted anal sex history was not associated with HPV prevalence.
Dr. Kojic and colleagues also determined that most of the high-risk HPV types “detected in abnormal anogenital cytologies were types included in the 9v vaccine [Gardasil 9], and because its use might impact the clearance rates of HR-HPV (high-risk HPV) by decreasing the overall burden of anogenital HPV infection in HIV-infected women, these findings further support use of the nonavalent vaccine [Gardasil 9],” which is probably the most important and clinically relevant finding of the study.