Researchers say the vaccine given in the United States from 2006 to 2015 reduced two common HPV strains.
There is some encouraging news in the fight to eliminate cervical cancer in the United States.
According to a new study published in the journal Cancer Epidemiology, Biomarkers & Prevention, two strains of the human papillomavirus (HPV) linked to cervical cancer have declined thanks to the vaccine developed to combat the disease.
“This study is really important because it shows the HPV vaccine is working to prevent cervical disease in young women in the United States,” Nancy McClung, PhD, an epidemic intelligence officer at the Centers for Disease Control and Prevention (CDC), told Healthline.
The data comes from an ongoing CDC surveillance system called the HPV Vaccine Impact Monitoring Project.
Dr. McClung and her colleagues analyzed more than 10,000 cases collected between 2008 and 2014. The women, ages 18 to 39, had been diagnosed with precancerous conditions that can come from HPV infection, and can lead to cervical cancer.
The researchers wanted to know whether HPV types 16 and 18, responsible for approximately 70 percent of cervical cancers worldwide, were decreasing.
Those two types had been targeted by the HPV vaccine given in the United States from 2006 to 2015.
“We saw a decrease from 53 percent in 2008 to 44 percent in 2014 among all women,” McClung said. “Among women who were vaccinated, the proportion decreased from 55 percent to 33 percent in 2014.”
What accounts for the decline in unvaccinated women?
McClung said it may be due to a phenomenon called “herd protection.” This is when a significant proportion of a population develops immunity to an infectious disease either through vaccination or prior infection. That overall immunity lowers the risk for unvaccinated people.
But researchers didn’t see that decline among women ages 35 to 39. That’s because most of those women at the time weren’t eligible for the vaccine.
The researchers also didn’t see a decline among Hispanic and Asian women. McClung said these two groups may have been less likely to be vaccinated once they reached adulthood.
“Vaccination rates in adolescents across all race ethnicities are high and actually highest in Hispanic and Asian women,” she said. “We wouldn’t expect to see these differences decline in the future.”
Tamika Felder is the founder of Cervivor, an advocacy, support, and educational online community for cervical cancer survivors.
“As a 17-year cervical cancer survivor, I’m thrilled at the results of this study,” Felder told Healthline. “It proves what we already know, that the HPV vaccine prevents cancer.”
“Far too many women die from cervical cancer, and those of us lucky to survive it deal with many secondary health issues as well as the emotional trauma of having cancer itself,” she said. “Why not prevent this with a safe, effective vaccine.”
The results of the U.S. study come as scientists are learning new information about what it will likely take to eliminate cervical cancer around the world.
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However, researchers noted that low-income and middle-income countries are falling short.
Without further intervention, more than 44 million women will be diagnosed with cervical cancer in the next 50 years if prevention programs aren’t implemented in those countries, researchers said.
Australia, one of the first countries to introduce the HPV vaccine, has a high vaccine rate. Experts told Healthline in October that cervical cancer could be considered eliminated as a public health threat in that country in the next few years.
The success rate in the United States isn’t as high.
“It’s true that our coverage isn’t as high as in some other countries. But what this study specifically shows is that we’re seeing an impact from the vaccine,” McClung said. “Our coverage levels will hopefully continue to increase.”
She said vaccination coverage with HPV is still lower than that of other routine adolescent vaccines, but the rate is increasing every year.
“The most recent statistics show that 49 percent of girls and 37 percent of boys ages 13 to 17 are up to date on their recommended doses,” McClung said. “And those that have received at least one dose are higher than that.”
“This study has shown that the vaccine is working to prevent cervical disease. This can be important for doctors when talking with parents who may have questions,” McClung said.
“It’s important to know that in the future, we can expect an even greater decline in cervical precancers,” she said. “This will happen as more women are immunized at routine ages.”
Researchers say two strains of HPV linked to cervical cancer have declined since a vaccine against the disease was introduced.
The researchers focused on HPV types 16 and 18, responsible for approximately 70 percent of cervical cancers worldwide and targeted by the HPV vaccine, which was given in the United States from 2006 to 2015.
Researchers reported a decrease from 53 percent in 2008 to 44 percent in 2014 among all women, and from 55 percent to 33 percent in women who were vaccinated.