By Benjamin Ryan

A majority of Americans are unaware that HPV, the most common sexually transmitted infection in the U.S., can cause a number of major cancers, a new study found. Researchers were surprised over one finding in particular: a decline in awareness that HPV, human papillomavirus, is linked to cervical cancer.

Nearly all sexually active women and men become infected with HPV at some point, according to the Centers for Disease Control and Prevention. According to CDC estimates, currently more than 42 million Americans carry at least one strain of HPV. About 13 million people are infected each year.

In the new study, which will be presented Tuesday, researchers analyzed nationally representative survey data collected by the Health Information National Trends Survey that monitored U.S. adults’ knowledge about the virus’s connection to cancer. There were about 2,000 to 2,300 annual respondents to the survey, including for 2014 and yearly from 2017 to 2020.

They found that about two-thirds of respondents consistently had heard of HPV. Of that group in 2020, 70.2% were aware of the link between the virus and cervical cancer, a significant 7.4% drop from 77.6% in 2014.

“That was very shocking for us,” said lead author of the study Eric Adjei Boakye, an assistant scientist at the Henry Ford Health System in Detroit, of the falloff.

Only about 30% of the people who knew about HPV also knew it could cause throat or anal cancers.

Not all types of HPV are dangerous. Most infections don’t have symptoms and go away on their own within a couple of years. But in some cases, the infection persists and can lead to cancer.

About 47,000 people are diagnosed with HPV-linked malignancies annually, including cervical, anal, vulval, oropharyngeal (back of the throat), vaginal and penile cancer, according to the CDC. Cervical cancer is the most prevalent, with 13,800 cases of invasive cervical cancer diagnosed yearly in the U.S., according to the American Cancer Society. Precancerous cervical cells are diagnosed far more often.

The new findings come amid a surge of vaccine skepticism and a decline in child vaccination in the U.S. There’s long been resistance to the HPV vaccine, which was first approved in 2006 for girls and young women to prevent cervical cancer. It has since been updated to prevent anal, oral and head and neck cancer in men and women.

Much of the hesitation about the HPV vaccine is tied to fears about safety and a belief among a “substantial fraction of parents" that the vaccine isn’t necessary, a recent study found.

Some parents have resisted having their children vaccinated for HPV out of concern that it would encourage sexual risk taking. A 2018 study, however, found no association between state laws pertaining to HPV vaccination and school attendance and sexual behaviors in teens.

“One of the reasons why the vaccination rate is low is the fact that people are not aware that it actually prevents cancer,” said Adjei Boakye. “So there has been a lot of talk about trying to improve people’s awareness level.”

HPV vaccine can prevent cancer

Pre- and early-adolescent boys and girls have been the targeted group for receiving the HPV vaccine, although it has recently been cleared for people up to age 45.

“If we had nearly full vaccination rates, we could essentially eliminate these cancers, which would be spectacular,” said Dr. William L. Dahut, chief scientific officer at the American Cancer Society.

The current version of the vaccine prevents nine strains of HPV that are known to cause cancer.

Adjei Boakye and his coauthors speculate that the drop in awareness about HPV and cervical cancer may have been driven by efforts to educate doctors about recommending the HPV vaccine, rather than campaigns to educate the public.

He also theorized that online misinformation may be partially to blame. Despite persistent worries about safety, a study that reviewed Gardasil, the leading HPV vaccine, nine years following its approval, found no serious associated health outcomes after 178 million doses had been given worldwide.

“It might be one of the safest vaccinations we’ve ever had,” said Dahut.

Research suggests the HPV vaccine has already had a dramatic public health impact. In the mid-2000s, 11.5% of teenage girls carried at least one of the four HPV strains. That figure plunged to 1.8% a decade later, according to the CDC.

A recent study found a 65% drop in cervical cancer incidence during 2012 through 2019 among women in their early 20s, the first cohort to receive the HPV vaccine.

Various states have laws requiring HPV vaccination for adolescents’ school attendance, including Hawaii, Rhode Island, Virginia and Washington, D.C. California legislators recently proposed requiring all students entering the eighth grade to receive the vaccine.

Too late for HPV vaccine?

People who are already sexually active may still benefit from the vaccine, research suggests. Even if they have already contracted one or more of the cancer-linked strains, the vaccine may still prevent such individuals from contracting other strains, and thus could still mitigate their overall cancer risk.

During routine gynecological exams, doctors can look for cancerous or precancerous cells on the cervix through a Pap test. Left untreated, precancerous cells may progress to cancer.

Adjei Boakye emphasized that HPV vaccination is particularly vital as prevention for oral, penile and anal cancers, since there is no standard, recommended screening for early detection when the diseases are easier to treat.

“It’s always really shocking that people still think they don’t need it,” he said of the vaccine. “It’s a human thing, they think they will never get cancer.”