HPV vaccine has no therapeutic value against active HPV infection

August 14, 2007

NEW YORK (Reuters Health) - Human papillomavirus (HPV) vaccine does not accelerate clearance of HPV infections, investigators report in the Journal of the American Medical Association for August 13.

In a phase 3 trial, Dr. Allan Hildesheim from the National Cancer Institute in Rockville, Maryland, and associates tested the effect of HPV 16/18 L1 viruslike particle (VLP) vaccine in women with active HPV infections living in two provinces of Costa Rica.

The subjects, ages 18 to 25 years, were stratified according to HPV-16/18 serology, cytologic results, HPV DNA viral load, time since sexual debut, Chlamydia trachomatis or Neisseria gonorrhoeae infection, hormonal contraceptive use, and smoking.

They were then randomly assigned to immunization with the HPV vaccine (n = 1088) or a control hepatitis A vaccine (n = 1101), each administered as three doses over 6 months.

Dr. Hildesheim and associates observed no evidence of increased viral clearance with HPV vaccination. Clearance rates of HPV-16/18 infection at 6 months were 33.4% in the vaccine group and 31.6% in the control group. At 12 months, rates were 48.8% and 49.8%, respectively.

The research team observed no significant differences among the prespecified subgroups. In addition, there were no therapeutic effects for other categories of HPV, either nononcogenic or oncogenic.

The research team points out that most HPV infections clear spontaneously, usually within 6 months to 2 years.

Dr. Hildesheim's group is concerned that women found to be HPV-positive may want to use HPV vaccine to treat their infection. "Our results indicate that clinicians should discourage use of L1 VLP-based vaccines for this purpose," the investigators say.