High Effectiveness and Increased Vaccination Rates Mark Success of HPV Vaccine

In the 10 years since the human papilloma virus (HPV) vaccine first became available, a series of new studies have come out showing just how effective the virus really is and how HPV vaccination rates can be improved in adolescents.

While little was known about the virus a few decades ago, HPV and its impact on human health came to light when years of research culminated in the 1995 International Biological Study on Cervical Cancer Group’s finding that 93% of cervical cancer specimens contained HPV DNA. Further studies found that HPV causes more than 99% of cervical cancers. Now, more than 80 million people in the United States are currently infected with HPV. According to the Centers for Disease Control and Prevention (CDC), there are more than 150 identified forms of HPV, and each strain is denoted with a number. While cervical cancer— largely from HPV 16 and HPV 18– is the most common cancer caused by HPV infections, they can also lead to vulvar, vaginal, penile, anal, and throat cancers. The World Health Organization notes that in 2008 there were more than half a million new cases and 274,000 deaths from cervical cancer, and virtually all of those cases are linked to persistent genital HPV.

Officials at the World Health Organization stress that the HPV vaccine is an important tool when it comes to the eradication of these preventable cervical cancers. There are some 14 million new cases of HPV each year, and to curb that, the CDC recommends that children receive the full HPV vaccine series at age 11 or 12, well before they become sexually active. Doctors administer the vaccine in a series of three shots, which when given during the preteen years, incites a stronger immune response. Young women and men can receive the vaccine through age 26 and 21 respectively.

A new study published in JAMA Oncology, shows that since the introduction of the HPV vaccine there has been a significant reduction in the rates of high-grade cervical intraepithelial neoplasia (CIN), which is caused by persistent HPV infection and can lead to invasive cervical cancer. The study analyzed data collected from women ages 15 to 29 from January 1, 2007 through December 31, 2014, in the New Mexico HPV Pap Registry, a surveillance program on cervical screenings for women in the state. The researchers studied rates of CIN grade 1 (CIN1), CIN grade 2 (CIN2), CIN grade 3 (CIN3), carcinoma in situ, and adenocarcinoma in situ. By 2014, about 40% of women ages 13 to 17 had received all three doses of the HPV vaccine and the researchers found a correlating and significant population-level decrease in the incidence rate of all grades of CIN for female individuals 15 to 19 years old, and in the incidence of CIN2 for women 20 to 24 years old. In women between the ages of 15 to 19, rates of CIN1 and CIN2 dropped by more than 50% and the reported cases of CIN3 dropped from 240 to none.

“Reductions in the incidence were greater than anticipated based on HPV vaccination coverage in the population and the proportions of CIN attributable to HPV types directly targeted by the vaccine (HPV-6, HPV-11, HPV-16, and HPV-18),” write the authors. “Cross-protection against non-vaccine HPV types, efficacy of less than 3 vaccine doses, and herd immunity may likely be contributing to these observations.”

Another study, published in the journal Pediatrics, looked at ways to increase the rate of adolescent girls and boys receiving the full course of the HPV vaccine, which has lagged below vaccination rates for other diseases. Researchers at Denver Health, an integrated organization with over 17,000 adolescent patients, noted a vaccination rate of more than 95% for tetanus, diphtheria, and pertussis in their patients, and more than 93% coverage for the meningococcal conjugate vaccine. Through a combination of “bundling” the HPV vaccine with other vaccines, offering vaccines at every visit, and issuing/following standard orders, the health system was able to achieve high rates for HPV vaccination. During their study, conducted from 2004 to 2014, the researchers were able to get more than 89% of their female patients vaccinated with at least one dose of the HPV vaccine, while national rates were at 57.3% for females and 34.6% for males. For all three doses of the vaccine, Denver Health achieved a coverage rate of 66% in females and 52.5% in males, faring better than the national average of 37.6% for females and 13.9% for males. The strategy was successful, note the study authors, because it took advantage of every opportunity for vaccination and normalized the HPV vaccine.

With improved HPV vaccination rates in adolescents now a big focus, another recent study, in the journal Cancer Epidemiology, Biomarkers & Prevention, highlights the role that a doctor’s words can play in encouraging a parent to have their child immunized. The study looked at how parents responded to doctors presenting motivational materials for vaccination prepared by the CDC, along with additional messages developed by the research team. Included in the study were 776 primary care doctors and more than 1,500 parents. They found that parents who initially declined the HPV vaccine responded more to messages that contained information regarding how common cases of HPV are, the different cancers that can result from HPV, and how effective the HPV vaccines are. The most effective message, found to be persuasive in 65% of parents, read, “I strongly believe in the importance of this cancer-preventing vaccine for [child's name].” Messages that emphasized parents' role in preventing their child from receiving HPV infections and related cancers decreased hesitancy about the vaccine.

The CDC emphasizes the safety of the HPV vaccine, noting that its development included years of safety testing before receiving approval from the US Food and Drug Administration. Current data shows that the HPV vaccine works in the body for at least 10 years without becoming less effective and can still be effective beyond that period of time.