A new study has found that the human papillomavirus (HPV) vaccine is not effective in preventing the spread of the virus in women who are already infected.
In a research conducted among women aged 18 to 25 with proven exposure to the sexually transmitted virus, investigators found that the vaccine didn't help clear the virus from their bodies.
HPV has been linked to the development of cervical cancer, and the vaccine, which just recently became available, is considered a new forefront protection against the disease.
Allan Hildesheim, Ph.D., of the National Cancer Institute, Bethesda, Md., and colleagues conducted a study to address the question of whether women positive for HPV DNA should be encouraged to receive HPV-16/18 vaccination to induce or accelerate clearance of their infections.
In the trial, 2,189 women were randomly assigned to receive three doses of HPV-16/18 vaccine or a control hepatitis A vaccine over 6 months.
The results showed there was no evidence that HPV vaccination significantly altered rates of viral clearance. At the 6-month visit, rates of clearance were 33.4 percent vs. 31.6 percent for HPV-16/18 among participants who received the HPV vaccine and the control vaccine, respectively. At the 12-month visit, rates of clearance among participants in the HPV group and the control group, respectively, were 48.8 percent vs. 49.8 percent for HPV-16/18.
There was no proof of vaccine effects with further analysis on selected study entry characteristics reflective of disease extent, including HPV-16/18 antibody results, cytologic results, and HPV viral load. Likewise, no evidence of vaccine effects was observed in analyses stratified by other study entry parameters thought to potentially influence clearance rates and efficacy of the vaccine, including time since sexual initiation, oral contraceptive use, cigarette smoking, and concomitant infection with Chlamydia trachomatis or Neisseria gonorrhoeae.
"Our results demonstrate that in women positive for HPV DNA, HPV-16/18 vaccination does not accelerate clearance of the virus and should not be used for purposes of treating prevalent infections," the authors write.
In an accompanying article, Lauri E. Markowitz, M.D., from the Centers for Disease Control and Prevention, suggests the current findings point to the need to follow recommendations calling for girls to receive the vaccine before they are sexually active.
"These data, along with data demonstrating the high likelihood of acquiring HPV infection soon after onset of sexual activity and data on sexual behavior in the United States, all contributed to recommendations for routine immunization at 11 to 12 years of age. Because the vaccine has no therapeutic efficacy, the greatest effect will be realized if the vaccine is administered before sexual debut, prior to exposure to HPV," Markowitz writes.
The findings of the stud are published in the August 15 issue of JAMA.