According to a new study conducted by the U.S. Centers for Disease Control and Prevention, and published in The Journal of Infectious Diseases, HPV (human papillomavirus) infections in female teenagers (ages 14-19) have decreased by 56 percent since 2006 -- the year HPV vaccine began to be administered.
HPV is the most common sexually transmitted disease in the U.S., and is blamed for causing cancer (primarily cervical cancer) in 27,000 Americans each year.
The CDC study compared infection rates in girls ages 14 to 19 before and after the vaccine became available. The proportion infected with the targeted HPV strains dropped 56 percent, from about 12 percent before the vaccine was sold to 5 percent. That result was for all teens after it was on the market, whether or not they were vaccinated (italics added for emphasis).
According to the CDC, two-thirds of girls, ages 13 through 17, in the U.S. have not been fully vaccinated against HPV. Only about half of teen girls have received at least one does of the vaccine. Among girls who had gotten the vaccine, the drop in HPV infections was higher — 88 percent.
The drop in HPV infection rates in teen girls is welcome news, and there is little doubt that the vaccine has had a significant effect in the reduction. But, given that only a third of young females have received the full vaccination protocol, it would seem that the vaccine is not solely responsible for the falling rate of HPV infections. Still, media outlets may be creating their own narrative, as the Washington Post article implies:
"A vaccine against a cervical cancer virus cut infections in teen girls by half in the first study to measure the shot’s impact since it came on the market."
And so we are led to believe it's all due to the vaccine, despite two-thirds of girls having not been fully vaccinated.
The Washington Post article goes on to posit that although only a third of girls studied had received the vaccine, the significance of the reduction "could be due to “herd immunity” — when a population is protected from an infection because a large or important smaller group is immune," and "that a higher percentage of vaccinated teens said they’d had three or more sex partners...," "which could have driven down infection rates if the teens who got vaccinated were the ones at highest risk of getting an infection and spreading it."
The argument seems plausible, but it seems to be a jump to reach the conclusion the vaccine is solely responsible. What we know (and can be encouraged by) is that HPV infections are down 56 percent.
The CDC recommends routine HPV vaccination for both boys and girls ages 11 and 12, as well as for older teens and young adults who have not previously received the vaccine (up to age 21 for males and 26 for females).