HPV Vaccine Cervarix Also Protects From Anal Cancer

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Academic Journal
Main Category: Cervical Cancer / HPV Vaccine
Also Included In: Cancer / Oncology;  Women's Health / Gynecology
Article Date: 22 Aug 2011 - 20:00 PDT


GlaxoSmithKline's bivalent HPV vaccine Cervarix offers strong protection against anal cancer, even though it is used as a routine vaccination for girls against cervical cancer, researchers reported in The Lancet Oncology.

Significant effects were noted in women who received the vaccine before exposure to the virus.

Even though anal cancers are still uncommon in the general population, recent decades noted almost double the amount of cases in many countries including the USA and Europe. Anal cancer is twice as common in women compared to men, with a large proportion of anal cancers being caused by HPV, with high-risk types HPV 16 and HPV 18 responsible for 75-80% of anal cancers.

Routine vaccination of girls against cervical cancers with the bivalent vaccine targets HPV types 16 and 18 and could offer additional protection against anal cancers associated with HPV infection.

Aimée Kreimer of the National Cancer Institute, National Institutes of Health in Bethesda, USA, and her colleagues examined the effectiveness of the bivalent vaccine to reduce anal HPV 16 and HPV 18 infection with data from a randomized trial of women in Costa Rica, consisting of 4,210 healthy women aged 18-25 years.

The researchers assigned the women randomly to be administered with the bivalent HPV vaccine or a control (Hepatitis A) vaccine. The vaccines were given in three stages, once at enrolment, then at 1 month, and again at 6 months. 4 years later, the women were tested for anal and cervical HPV 16 and 18 infections to see how effective the vaccine was.

Irrespective of prior exposure to HPV, the vaccine showed a 62% efficacy against HPV anal infection in the general population of young women, compared with nearly 77% efficacy against HPV cervical infection.

The vaccine prevented anal HPV infection in nearly 84% of women who probably had no exposure to previous HPV infection. A similar result, nearly 89%, was noted in the vaccine's efficacy against cervical HPV infection (nearly 89%).

For the first time the vaccine also displayed cross-protective efficacy against other cancer-causing HPV types 31, 33 (not significant for HPV33), and 45 at an extragenital site, proving that the vaccine's protection goes beyond the HPV types included in the formulation.

The authors remark in a concluding statement:

"HPV vaccines have great potential for prevention of a large proportion of HPV-associated cancers at the anus and other anatomical sites, assuming adequate duration of protection. In women, published evidence exists for vaccine efficacy against HPV 16 and HPV 18 infections at the cervix, vagina, vulva, and now anus.

Since our data show a reduction of anal HPV infection rates among vaccinated women, it suggests that in the future, women who receive the prophylactic HPV vaccines before exposure to the virus will likely have less anal cancer."

Diane Harper and Stephen Vierthaler from the University of Missouri-Kansas City School of Medicine in Kansas City, USA, argue possible targets for the vaccination against anal cancer. They comment:

"The additional protection against four oncogenic anal HPV types in women increases their benefits from vaccination. For men who have sex with men, HPV vaccination for anal cancer prevention is very cost effective, but cost-effectiveness analyses for women and for men who have sex with men pivot on the duration of vaccine efficacy. Without duration of efficacy of at least 15 years, cancers will not be prevented for women or men who have sex with men, only postponed."

Written by Petra Rattue


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