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 Within six years of the U.S. vaccine debut in 2006, there was a 64
percent decline in the prevalence of four vaccine-preventable stains
of the virus among girls aged 14 to 19 and a 34 percent drop among
women aged 20 to 24, researchers report in the journal Pediatrics.
"HPV vaccination has the potential to prevent up to three out of
four HPV-associated cancers," said lead study author Dr. Lauri
Markowitz of the Centers for Disease Control and Prevention in
Atlanta.
HPV is among the most common sexually transmitted diseases. Most
infections don't cause symptoms and go away on their own, but the
virus is a still leading cause of cancer deaths among women
worldwide. It can also cause genital warts and lesions in the upper
respiratory tract.
In the U.S., the HPV vaccine is recommended for children at age 11
or 12 years, with the goal of protecting them against the virus
before they become sexually active, and also for teens and young
adults who may not have previously been vaccinated.
But just 40 percent of girls and 22 percent of boys have received
the three-dose series of shots needed to fully protect against the
virus, Markowitz added by email.
"National HPV vaccination rates are low, leaving girls vulnerable
not only to cervical cancer, but also to other cancers caused by HPV
infections (i.e. vaginal, vulvar, anal and oropharyngeal cancers),"
Markowitz added. "HPV infections can also lead to cancers of the
anus, penis, and oropharynx in boys, so these low rates also leave
boys vulnerable to HPV cancers."
To see how the vaccine influenced infections, Markowitz and
colleagues reviewed national health survey data from 2003 to 2006,
before the vaccine debut, and compared it to data from 2009 to 2012.
The prevalence of HPV among females aged 14 to 19 dropped from 11.5
percent before the vaccine was available to 4.3 percent afterwards.
For women aged 20 to 24, prevalence declined from 18.5 percent to
12.1 percent.
Before the vaccine became available, the prevalence of
vaccine-preventable strains of HPV was 18.6 percent among sexually
active 14 to 24 year olds. After the vaccine was introduced, the
prevalence dropped to 2.1 percent among those who got vaccinated but
only dipped to 16.9 percent among those who didn't get vaccinated.
While the results highlight the effectiveness of the vaccine in
slowing the spread of HPV strains, adoption of the vaccine has been
slower than expected, the authors note.
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Many girls and boys don’t receive the vaccine at least in part
because their parents may question whether it’s necessary to protect
them against a sexually transmitted disease at an age when they
think children shouldn’t be having sex, researchers say.
Beyond resistance to the vaccine from some parents, some
pediatricians may not prioritize this vaccine as much as
inoculations against other childhood diseases, researchers also
note.
"Doctors are not recommending it enough," Dr. Cora Breuner, an
adolescent specialist at Seattle Children's Hospital who wasn't
involved in the study, said by email.
Healthcare providers need to take the time to help parents
understand the rationale behind the HPV vaccine, and stress that
children need it before they become sexually active to make it an
effective tool for cancer prevention, said Dr. Ruth Lynfield, a
pediatrics researcher and medical director of the Minnesota
Department of Health.
"HPV vaccine needs to be given prior to exposure to these viruses in
order to be effective in preventing infections with these viruses,
and there is also a good immune response to the vaccine in early
adolescence," Lynfield, who wasn't involved in the study, said by
email.
"It is fine if it is given many years before a person becomes
sexually active," Lynfield added. "It needs to be stressed that it
is a cancer prevention vaccine."
SOURCE: http://bit.ly/1UifRGM Pediatrics, online February 22, 2016.
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