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Although more adolescents are being vaccinated against human papillomavirus, adoption rates for the vaccine are still low in the United States, with 4 out of 10 girls remaining unvaccinated.
Antivaccination rhetoric is a hot topic, but a special kind of stigma surrounds the human papillomavirus (HPV) vaccine.
Some parents have refused to have their children vaccinated against HPV because they are reportedly afraid that vaccinating against a virus that is often sexually transmitted would encourage their children to become sexually active, or increase their level of sexual activity. Despite studies that have proven this assumption untrue, only 60% of adolescent girls and 40% of adolescent boys have started the recommended vaccination series, according to the Centers for Disease Control and Prevention (CDC).
The number of males and females aged 13 to 17 years who received the HPV vaccine increased over the last year-for the second year in a row-CDC announced last month. For girls, this means a 3% increase over the prior year, and an 8% increase for boys. Whereas the gains are a step in the right direction, researchers say adoption of the vaccine is still too low in the United States.
The CDC’s report plus a new study led by Pierre Van Damme, MD, PhD, on the efficacy and safety of the latest vaccine clarify information on adverse events and give guidance to clinicians who are working to educate parents and patients about HPV vaccination.
Of the more than 170 types of HPV identified, 15 are carcinogenic and 40 are transmitted through sexual contact. Although most HPV infections don’t cause disease, high-risk HPV infections are the cause of nearly all cases of cervical cancer. An estimated 12,900 cases of cervical cancer will be diagnosed this year and more than 4000 could die as a result.
Human papillomavirus causes premalignant and malignant lesions of the cervix, vagina, vulva, anus, penis, and oropharynx, and can also cause genital warts. According to the study, HPV is to blame for about 5% of cancers worldwide.
Widely recommended based on clinical trials and postlicensure data, HPV vaccines have been deemed as highly effective. The quadrivalent HPV (qHPV) vaccines are useful in preventing infections, as well as preventing cervical, vaginal, vulvar, and anal dysplasia, and condyloma related to HPV. The bivalent HPV vaccine is effective against infection and cervical dysplasia.
The Van Damme study focused on the 9-valent HPV vaccine (HPV9), marketed as Gardasil 9, which is recommended by CDC and the American Academy of Pediatrics (AAP).
The AAP updated its recommendation for HPV vaccination in May 2015, advising pediatricians to routinely administer HPV9. It is approved by the US Food and Drug Administration (FDA) for females aged 9 to 26 years and males aged 9 to 15 years. The AAP notes that routine immunization for both girls and boys is ideal at 11 or 12 years of age, but can be begun as early as age 9.
The vaccine is given over a 3-dose regimen, with the second and third doses given at ages 2 and 6 months, respectively. Van Damme’s study followed more than 3000 subjects, and 40.9% were positive for at least 1 vaccine HPV type at the time of vaccine administration. A review, which occurred 3 years after the last dose was given to study subjects, reveals that more than 90% were seropositive for each of the 9 HPV types covered under the HPV9 vaccine.
The rate of adverse events was low, with only 2 serious adverse events reported in the entire study group. One was an asthma exacerbation in a 10-year-old boy with a history of seasonal and bronchial asthma, 1 day after receiving dose 1 of the vaccine. He later made a full recovery. The other serious event was in a 21-year-old woman with a severe headache and neck stiffness on the day she received her third vaccination dose. She was later hospitalized and diagnosed with a viral infection or adverse event related to the vaccination.
Typical adverse events included injection site pain, swelling or erythema, itching, and some headaches. The study notes that injection-site or systemic reactions were less frequent in younger boys and girls in the study group compared with older young women.
The study was the first examination of the HPV9 vaccine’s immunogenicity in girls and boys aged 9 to 15 years-the primary target for vaccination.
“The antibody responses in 9- to 15-year-old boys and girls was shown to be non-inferior to those observed in 16- to 26-year-old young women (the population used to establish 9vHPV vaccine efficacy), thereby supporting the bridging of efficacy findings from 16- to 26-year-old women to 9- to 15-year-old boys and girls,” Van Damme wrote in the study. “Antibody responses for all vaccine HPV types were numerically greater in girls and boys than in young women.”
Van Damme also notes that the vaccines were generally well tolerated, and immunity persisted over time. Long-term studies reaching 96 months post-vaccination suggest HPV9 can offer long-term protection, Van Damme says.
Ann-Christine Nyquist, MD, MSPH, a member of the AAP Committee on Infectious Diseases, says Van Damme’s study is important because of the bridging aspect, which could help clinicians when educating parents about administering the vaccines at a younger targeted age.
“[This study] is important because it shows that the new HPV9 vaccine provides a robust immune response in boys and girls aged 9 to 15 years when compared to young women and is safe and well-tolerated by the children vaccinated,” Nyquist says. “This information meets the requirements for the vaccine immune response in this age group to be ‘bridged’ because the younger age patients do not have evaluations for the end outcome of HPV infection and cancer as the young women do.”
The study also reveals a lot about the adverse events associated with the HPV vaccine, she says, as well as how well children generally tolerated the vaccine. Additionally the vaccine was closely monitored in this study for adverse events and found local injection site pain, swelling, itching, and redness that was well tolerated by the children vaccinated.
“Both the AAP and the CDC Advisory Committee on Immunization Practices agree that HPV vaccine should be recommended by pediatricians and other healthcare providers for routine immunization along with Tdap and meningococcal vaccine at ages 11 and 12,” Nyquist says. “The message to families needs to be that vaccination at this time gives a very good immune response (in fact a better immune response than older adolescents and adults), is safe, and prevents HPV-related cancers.”
The CDC notes that despite ongoing educational efforts, adoption of routine vaccination against HPV is still low in the United States.
Older females were more likely to both begin and complete the HPV series, according to the CDC. A few pockets of the country saw significant increases in HPV vaccination rates, says the CDC, and those areas employed combination strategies, incorporating a push for HPV vaccination into cancer prevention programs, immunization programs, and other public communications.
Recommendations from healthcare providers are crucial to getting parents to have their children vaccinated against HPV, says the CDC. The agency asks clinicians to recommend the HPV vaccine the in the same manner as other adolescent vaccinations.
Van Damme recommends in his report that gender-neutral HPV vaccination guidelines should be implemented in preadolescents and adolescents.