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Study shows sharp decline in HPV infections since introduction of vaccine

A new study of young women in the United States found that prevalence of human papillomavirus (HPV) in young women had dropped significantly six years after the introduction of HPV vaccine.

The study results showed a sharp decrease in the types of HPV infection targeted by the vaccine. In young women ages 14 to 19, prevalence of targeted HPV types dropped by 64 per cent since the introduction of the vaccine. In women ages 20 to 24, the decrease was 34 per cent.

HPV is sexually transmitted, and there are dozens of specific types of the virus. Most types cause no symptoms, but some types of HPV can lead to cervical cancer, while others cause genital warts.

Vaccines that protect against specific strains of HPV were introduced in the U.S. in 2006. One vaccine protects against types 16 and 18, which are implicated in the majority of cervical cancers. This is called a bivalent vaccine. Another vaccine protects against types 16 and 18, as well as types 6 and 11, which are responsible for the majority of genital warts. This is called a quadrivalent vaccine. A new vaccine targeting a total of nine types of HPV was introduced in 2014.

Vaccination programs were aimed at girls ages 11 or 12, and young women up to age 24.

Researchers at the Division of STD Prevention of the Centers for Disease Control in Atlanta, Georgia looked at prevalence of HPV infection in young women ages 14 to 34, before and after the vaccine was introduced. They used samples collected from 2,587 women in the pre-vaccine era (2003-06), and 2,061 women in the post-vaccine era (2009-12). They tested for 37 different types of HPV.

Of the women tested in the post-vaccine era, only about half of women ages 14 to 19 had been vaccinated, and only about one-third of women ages 20 to 24. However, the decrease in HPV infections for the types targeted by the quadrivalent vaccine was significant in both age groups. There was no significant decrease in infections in older women, who had much lower vaccination rates.

In the 14 to 19 age group, prevalence of the four vaccine-targeted HPV types dropped from 11.5 per cent to 4.3 per cent. In the 20 to 24 age group, prevalence dropped from 18.5 per cent to 12.1 per cent. There were no decreases in other HPV types not targeted by the vaccine.

The sharp decreases in HPV prevalence remained when the researchers limited the analysis to women who were sexually active.

These results add to a growing body of research supporting the effectiveness of vaccination in preventing infection with HPV types associated with cervical cancer and genital warts.

The study, which was led by Dr. Lauri E. Markowitz, was published in the journal Pediatrics on Feb. 22, 2016.

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  • A publication of:
  • Women's College Hospital