July 9, 2012
HPV Vaccines Reducing Infections Even Among Unvaccinated
The human papillomavirus (HPV) vaccine is reducing
infections of certain strains of HPV even among girls and young women who are
not vaccinated, according to a study published in the journal Pediatrics and
reported by HealthDay News.
HPV is a virus known to cause genital warts and cervical
cancer and is the most common sexually transmitted infection in the United
States. The HPV vaccine works by preventing the most common types of HPV, and it’s
recommended for all teen girls and women younger than 26. It’s most effective
when individuals receive all three doses of the vaccine before becoming
But a new study is showing that the vaccine not only
prevents infections but also promotes what is known as “herd protection”—a
decrease in infections among those who are not immunized. This is due to the
lower rates of infection among others who might be transmitting the disease.
For the study, researchers looked at two groups of women ages
13 to 26, all of whom had already had sexual contact. One group was seen between
2006 and 2007—before the HPV vaccine was available—and the second group was
seen between 2009 and 2010, after vaccines were readily available. About 60
percent of participants in the second group had received the vaccine.
Researchers found that from 2006 to 2010, the prevalence of
the four most common strains of HPV decreased by about 60 percent, from about
32 percent to 13 percent. And among individuals who were vaccinated, rates of
HPV infection fell from 32 percent to 10 percent. Most important, rates of
infection among unvaccinated individuals fell from 30 percent to 15 percent—a
50 percent drop.
“This is a first look at how the vaccine is working in a
real-world setting,” said Jessica Kahn, associate professor of pediatrics at
Cincinnati Children’s Hospital Medical Center. “We were very encouraged to find
the rates of HPV fell so dramatically, especially because the girls in the
study already had sexual contact, some had more than one sexual partner and
some only had one dose to be considered vaccinated.”
Why did researchers find such a dramatic drop?
“If girls are getting vaccinated, they are not spreading HPV
to male partners, who then don’t spread it to other female partners,” Kahn
However, although the prevalence of the four main HPV
strains fell, the overall rate of HPV infection remained high. Infection by any
HPV strain increased from 61 percent to 76 percent during the study’s two time
periods, which researchers said highlights the need for vaccines.
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