The impact of the human papillomavirus vaccine may go beyond those who are vaccinated—it could offer protection for those haven’t even gotten inoculated, a study finds.
The phenomenon is called herd protection or herd immunity, and it refers to a level of protection against contagious diseases that results from a substantial number of people getting vaccinated.
In the study released online today in the journal Pediatrics, researchers looked at two populations of sexually active teens and young women from two clinics in Cincinnati. The first group of 368 was recruited in 2006 and 2007 and made up of women who were not vaccinated. The second group of 409 was recruited in 2009 to 2010. Almost 60 percent of girls and women in that group had gotten the HPV vaccine.
The vaccine given at the time was the quadrivalent HPV vaccine (known as Gardasil), a three-dose series that prevents four types of HPV. In addition to shielding against cervical cancer, the vaccine also guards against genital warts and cancers of the vagina, vulva, and anus.
In general, incidence of vaccine-type HPV dropped 58 percent, from 31.7 percent to 13.4 percent. Those who had been vaccinated reaped the biggest benefits—their rates went down 69 percent.
But a 49 percent decrease was seen among unvaccinated women as well.
“The results are promising in that they suggest that vaccine introduction could substantially reduce rates of cervical cancer in this community in the future,” said lead author Dr. Jessica Kahn in a news release.
Despite the encouraging figures, Kahn added that it’s still important for young women to get the vaccine. In the study, although vaccine-type HPV numbers went down, almost one in four unvaccinated participants tested positive for at least one high-risk type of HPV.
The Centers for Disease Control and Prevention recommends the HPV vaccine for girls and boys at age 11 or 12. The agency also recommends the vaccine for females age 13 to 26 and males age 13 to 21 who haven’t been vaccinated or didn’t completed the series of shots.