There's growing evidence that the HPV vaccine can protect even young women and girls who haven't been immunized.
A new government study finds human papillomavirus infections have declined dramatically in both vaccinated and unvaccinated teen girls and young women.
Data from a national database reveal an 88 percent decline in the prevalence of the HPV strains targeted by the vaccine in girls ages 14 to 19 and an 81 percent decline in young women ages 20 to 24, compared to a time period before 2006, when the vaccine was released in the United States, Centers for Disease Control and Prevention researchers reported Thursday.
“This is really exciting,” said the study’s lead author Dr. Hannah Rosenblum, a medical epidemiologist at the CDC. “This report shows the high effectiveness of the vaccine.”
HPV, or human papillomavirus, is the most common sexually transmitted infection in the U.S., according to the CDC. There are many different types of HPV, but certain strains can cause cervical cancer in women and head and neck and penile cancers in men and anal cancer in both men and women. In 2018, an estimated 23.4 million men and 19.2 million women in the U.S. were infected with HPV strains linked to cancer. Most become infected in their late teens and their early 20s.
The CDC recommends two doses of the HPV vaccine for all girls and boys ages 11 to 12, but says the vaccine can be given as early as age 9. Data from 2019 showed that 72 percent of girls ages 13 to 17 had received one or more doses of the vaccine, Rosenblum said. And 54 percent had completed the series of shots.
To take a closer look at the impact of the vaccine, Rosenblum and her colleagues turned to the National Health and Nutrition Examination Survey, or NHANES, an ongoing cross-sectional survey conducted by the CDCs National Center for Health Statistics, which monitors the health and nutrition of the civilian population. Demographic and HPV vaccination information was obtained during home interviews. Sexual behavior information was obtained via audio computer-assisted self-interviews, while self-collected cervicovaginal specimens were obtained in mobile examination centers.
The data revealed that between 2015 and 2018, among sexually active girls ages 14 to 19 who had at least one shot, HPV strains targeted by the vaccine declined by 97 percent compared to the pre-vaccine era. Among sexually active women ages 20 to 24 who had at least one shot, HPV strains targeted by the vaccine declined by 86 percent compared to the period before 2006.
Among sexually active teens and young women who had not been vaccinated, there was also a decline compared to before 2006. Among 14- to 19-year-old girls, infections with the HPV strains targeted by the vaccine fell by 87 percent, and among young women ages 20 to 24 there was a decline of 65 percent in infections with the HPV strains targeted by the vaccine.
“This is big news,” said Dr. Stephanie Blank, director of oncology at the Mount Sinai Health System. “When you’re doing a clinical trial, you don’t do a 10-year study. This study is giving the real-life impact of this vaccine.”
'Perfect example of herd immunity'
The new study provides “proof of principle,” she said. “My main message is more people should get it, and the more who get it, the better it will work. This is really primary prevention for cancer.”
Parents and young adults need to “take advantage of this phenomenal vaccine,” said Dr. Robert Ferris, director of the UPMC Hillman Cancer Center in Pittsburgh. “The vaccine can prevent cancers like the anal cancer that Farrah Fawcett died of and cancers of the throat like the one Michael Douglas got treated for.”
“We don’t yet have all the cancer outcomes yet, but this is showing HPV vaccination is a prevention tool against infection and [the associated] cancers and pre-cancers,” Ferris said.
The finding that teenage girls and young women who did not get the vaccine “have been benefiting from it, is a perfect example of herd immunity,” said Dr. Nina Shapiro, a professor of head and neck surgery at the David Geffen School of Medicine at UCLA and author of “Hype: A Doctor’s Guide to Medical Myths.”
Herd immunity happens when enough of a population is immune to a disease, either through vaccination or prior illness, so that even individuals who are not vaccinated are offered some protection, according to the CDC.
“Now that boys are being immunized too, we will start seeing a bigger benefit to the unimmunized girls from this vaccine,” Shapiro said. “Some parents don’t understand why you would give a vaccine to 12-year-olds to prevent a sexually transmitted disease. They are equating it with giving a 12-year-old a condom. But this is a cancer-preventing vaccine.”