In the four years following the 2006 introduction of the human papillomavirus (HPV) vaccine, the prevalence of HPV infection — the most common sexually transmitted disease in the United States — dropped by half in adolescent girls, according to a study published Wednesday by the Centers for Disease Control and Prevention (CDC).
This decline was much higher than public-health officials had expected. Officials hope the results will encourage more adolescents to receive the vaccine.
“Unfortunately, only one third of girls aged 13-17 have been fully vaccinated with HPV vaccine,” noted Dr. Tom Frieden, director of the CDC, in a press statement. “Countries such as Rwanda have vaccinated more than 80 percent of their teen girls.”
A serious health concern
About 79 million Americans, most in their late teens and early 20s, are infected with the HPV virus, according to the CDC. The infection usually goes away on its own, and most people never realize they’ve had the virus. But in some cases, an HPV infection leads to serious health problems, including several types of cancer.
HPV is the main cause of the 19,000 annual cases of cervical cancer that develop in American women. It also causes 8,000 cases of cancers in American men each year, mostly oropharyngeal (throat) cancer. Other cancers associated with HPV include those of the vagina, penis and anus.
In addition, all cases of genital warts and recurrent respiratory papillomatosis (a rare condition in which warts grow in the throat) are caused by HPV.
In late 2006, the CDC’s Advisory Committee on Immunization Practices recommended girls aged 11 and 12 receive three doses (injections) of the HPV vaccine. They also advised adolescents and young women between the ages of 13 and 26 to get a catch-up version of the vaccine. In 2011, the ACIP recommended the vaccine for boys aged 11 and 12.
There are dozen of types of HPV. The two vaccines currently available — Gardasil (Merck & Co.) and Cervarix (GlaxoSmithKline) — protect against most HPV-related cancers, and one (Gardasil) also protects against genital warts.
For the new study, CDC researchers used National Health and Nutrition Examination Survey (NHANES) data to compare HPV prevalence among American women aged 14-59 in the three-year periods before (2003-2006) and after (2007-2010) the introduction of the HPV vaccine. More than 8,000 women were included in the study. In addition to answering survey questions, the women provided vaginal swabs that were then analyzed by the CDC.
The researchers found that among teenage girls (aged 14 to 19), the prevalence of HPV infections covered by the vaccines fell from 11.5 percent in 2003-2006 to 5.1 percent in 2007-2010, or a decline of 56 percent.
A closer look revealed that among the girls who had received the vaccine, the drop in infections was 88 percent.
Significantly, no decreases were observed in the other (non-vaccinated) age groups.
These results occurred despite the fact that most young women are not getting vaccinated against HPV. The CDC researchers found that only 49 percent of young women aged 13 to 17 had received at least one dose of the vaccine, and only 32 percent had received all three doses.
Growing parental resistance
Nor is the compliance trend encouraging. A study published earlier this spring in the journal Pediatrics by Dr. Robert Jacobson of the Mayo Clinic in Rochester reported that four in 10 families have decided not to have their teenagers vaccinated against HPV. Some of those parents said they believed the HPV vaccine was “not necessary” for their child. Most, however, cited concerns about safety or side effects. Despite assurances from the CDC, the American Academy of Pediatrics, and American Academy of Family Physicians and other child-health experts that the HPV vaccine is safe, Jacobson and his colleagues found that parental safety concerns about the vaccine almost quadrupled between 2008 and 2010, from 4.5 percent to 16.4 percent.
Those concerns have been fueled by false and misleading information about the vaccine, including the totally discredited 2011 statement by Rep. Michele Bachmann, R-Minn., that the HPV vaccine had caused at least one child to become intellectually disabled. But, as I’ve noted here before, the questionable early marketing tactics of the vaccines’ manufacturers have also hindered parental compliance.
Frieden hopes this study will be a “wake-up call” for parents and young women.
“Our low vaccination rates represent 50,000 preventable tragedies — 50,000 girls alive today will develop cervical cancer over their lifetime that would have been prevented if we reach 80 percent vaccination rates,” Frieden pointed out in his statement. “For every year we delay in doing so, another 4,400 girls will develop cervical cancer in their lifetimes.”
The CDC report was published in the June issue of the Journal of Infectious Diseases.