WEDNESDAY, Sept. 30, 2020 (HealthDay News) -- Girls who are vaccinated against human papillomavirus (HPV) may drastically cut their chances of developing cervical cancer by age 30, a huge, new study finds.
Researchers found that of more than 1.6 million young Swedish women, those who'd gotten the HPV vaccine were about two-thirds less likely to be diagnosed with cervical cancer than their unvaccinated peers.
Those odds were further slashed when the vaccine was given before age 17. Among those women, the risk of cervical cancer was 88% lower.
Experts said the findings, published Oct. 1 in the New England Journal of Medicine, support longstanding recommendations: Girls should be vaccinated against HPV before their teenage years.
"These findings aren't surprising. This is what we'd expect to see, based on what we know about this vaccine," said Dr. H. Hunter Handsfield, a professor emeritus of medicine at the University of Washington in Seattle.
HPV is a sexually transmitted disease that can cause genital warts. While that disease is usually minor, certain HPV infections can become persistent and eventually cause cervical cancer. So the HPV vaccine is considered an anti-cancer vaccine.
But, Handsfield said, it takes many years to go from HPV infection to cancer. So studies have first had to look at shorter-term effects of the vaccine -- finding that it prevents HPV infection, as well as precancerous abnormalities in the cervix.
The new findings are further confirmation the vaccine works, said Handsfield, who is also an adviser to the American Sexual Health Association.
HPV is the most common sexually transmitted disease in the world -- so common that nearly all sexually active people will contract the virus unless they are vaccinated, according to the U.S. Centers for Disease Control and Prevention.
Most of the time, the immune system is able to clear HPV infection. But some strains of the virus become persistent in a minority of people -- and, over time, may lead to certain cancers.
In the United States, nearly all cases of cervical cancer are caused by persistent HPV infection, the CDC says.
So since 2006, U.S. experts have recommended that girls receive the HPV vaccine, as early as age 9 and by age 12. If they miss that window, older girls and young women up to age 26 can receive "catch-up" shots. The advice was later extended to boys and young men -- since HPV can also cause cancers of the penis, anus and throat.
In Sweden, where the new study was done, recommendations are similar, and the government has paid for a school-based HPV vaccination program for girls ages 10 to 12 since 2012.
The study authors, who were led by researcher Jiayao Lei from the Karolinska Institute, looked at medical data on over 1.6 million Swedish women and girls who were between the ages of 10 and 30 from 2006 through 2017.
Of the group, about a half-million received at least one dose of the HPV vaccine.
Overall, the study found, those women were much less likely to develop cervical cancer by age 30. There were 47 cases per 100,000 women, versus 94 cases per 100,000 among women who were unvaccinated.
The biggest impact, though, was seen among women who'd been vaccinated before age 17. In that group, there were only 4 cases of cervical cancer per 100,000 women.
That throws even more weight behind early HPV vaccination, Handsfield said.
Debbie Saslow, managing director of HPV and GYN Cancers for the American Cancer Society, agreed.
She, too, said the findings were expected. "On the one hand, we knew this," Saslow said. "But this shows it definitively. Women who were vaccinated before age 17 had a nearly 90% lower risk of cervical cancer."
In the United States, the HPV vaccine is recommended, but unlike in Sweden, there is no national school program for administering it.
"Other countries do a better job of vaccinating than we do," Saslow said.
Things have been improving, however, she noted: A 2019 government study found that about two-thirds of U.S. teens had received at least one dose of the HPV vaccine. The worry, Saslow said, is that the progress will be reversed by the pandemic -- which has caused childhood vaccinations overall to plummet.
Saslow encouraged parents not to delay HPV vaccination.
"It prevents six types of cancer," she said. "Who wouldn't want to protect their kids from cancer?"
The American Cancer Society has more on HPV vaccination.