Widespread HPV vaccine use expected to take time

Despite a system that would mandate human papillomavirus vaccine for school, it will probably take years before a large percentage of adolescent girls are vaccinated, according to a speaker at the 43rd National Immunization Conference, held in Dallas this week.

Amanda Dempsey, MD, PhD, MPH, of the Child Health Evaluation and Research Unit of the University of Michigan, and colleagues developed what she termed a “more realistic” mathematical model that looked at HPV uptake among adolescent girls over a 50-year period.

She said mathematical models so far have predicted great reductions in projected cervical cancer and genital wart rates assuming that there was widespread uptake of the vaccine. However, she said these models may have overestimated these outcomes given the realities involved in actually getting adolescents into the office for well child care visits, where vaccines like HPV are typically administered.

Under nonmandated conditions, the researchers estimated 25% of adolescent girls would receive the first dose of vaccine, 17% would have received two doses and 7% received all three one year after vaccine introduction. After 10 years, the model predicted 57% of the recommended vaccinees would have actually received all three doses of the vaccine. After 23 years, the researchers predicted 70% uptake of the vaccine. At 50 years, the researchers predicted 78% of those recommended to be vaccinated would have actually received the vaccine without school mandates. The researchers said those predictive models matched up closely with NIS teen survey data showing that in 2007, about 25% of 13 to 17 year-old-girls had received one dose and 7% received three doses.

Under the same conditions, with HPV school mandates, the model predicted the rates would jump to about a 70% rate of vaccinated girls at eight years and a 91% rate of vaccination at 50 years.

Dempsey said separate modeling studies are also looking at what would happen with those rates if boys were also vaccinated against HPV; but she said more work needs to be done on financing and infrastructure before a recommendation for boys would be implemented.

The FDA’s Advisory Committee on Immunization Practices is expected to be looking at HPV recommendations for boys later this year, after Merck applied for this vaccine in boys in December. – by Colleen Zacharyczuk

For more information:

Dempsey A. #38. National Immunization Conference. March 30-April 2, 2009; Dallas.