CASE Sexually active woman asks about the HPV vaccine
A 26-year-old woman delivered her first child 4 weeks ago. She has had 3 lifetime sexual partners and is now in a mutually faithful monogamous relationship with her partner. She has no known history of sexually transmissible infections. She received only one Pap test 3 years ago, and the cytology showed no abnormal cells. This cervical specimen was not tested for human papillomavirus (HPV) DNA. At the time of her postpartum appointment, she inquires whether she is a candidate for the HPV vaccine.
What should be your response?
Genital HPV infection is the most common sexually transmissible infection in the United States. This virus is the cause of multiple genital malignancies, including cancers of the vagina, vulva, penis, anus, and cervix. The organism is also now the major cause of oropharyngeal cancer.
Of the more than 200 different HPV types that have been identified, 12 have been defined as oncogenic (high risk), and 8 to 12 types have been defined as possibly or probably oncogenic. The HPV strain with the highest risk of progression to cancer is HPV 16. The strains HPV 16 and 18 are responsible for approximately 70% of cases of cervical cancer. Each year in the United States, approximately 11,500 new cases of invasive cervical cancer occur. Unfortunately, this malignancy is responsible for about 4,000 deaths annually. Worldwide, HPV causes approximately 690,000 cancers each year.1
To a large extent, most cases of HPV infection would be preventable if patients were to take advantage of the remarkably effective HPV vaccine that is now available. However, acceptance of the vaccine has been disappointing. In 2020, only about half of adolescents, age 13 to 15, had received the appropriate number of vaccine doses.1
As ObGyn physicians, we can take several measures, in concert with our pediatrician colleagues, to improve HPV vaccination rates. In this article, I review the development of the HPV vaccine and describe the components, indications, dosing schedules, contraindications, adverse effects, and cost of the vaccine.
HPV vaccine development and expansion
The first HPV vaccine introduced in the United States was the recombinant quadrivalent vaccine (Gardasil; Merck); it was approved by the US Food and Drug Administration (FDA) in 2006. This vaccine is composed of viral-like particles unique to HPV 16 and 18 (the 2 most common causes of cervical, penile, anal, and oropharyngeal cancer) and HPV 6 and 11 (the 2 most common causes of genital warts). The formulation is prepared in baker’s yeast, and it elicits a robust production of neutralizing antibodies.2
In 2009, the FDA approved the bivalent vaccine (Cervarix; GlaxoSmithKline Biologicals). This vaccine contains viral-like particles unique to HPV 16 and 18, and it also induces a robust immune response. The vaccine is prepared in insect viral vectors.2
Both the quadrivalent and bivalent vaccines are no longer available in the United States. The only HPV vaccine currently marketed is the recombinant 9-valent vaccine (Gardasil 9; Merck), which was approved by the FDA in 2014. This newer vaccine targets the original 4 viral HPV strains in the quadrivalent vaccine (16, 18, 6, 11) plus 5 additional oncogenic strains: 31, 33, 45, 52, 58.2-4 The HPV strains targeted by this vaccine are responsible for approximately 90% of all cancers caused by HPV.
The 9-valent HPV vaccine, like the other 2, is highly effective in preventing cancers of the cervix, vagina, vulva, anus, penis; oropharyngeal cancers; and precancerous lesions such as genital warts.2-5 It will not, however, prevent the progression of preexisting infection or clear an infection that is already present at the time of vaccination.1
Although the original protocol for administration of the vaccine provided for 3 doses, recent studies indicate that 2 doses may be as effective as 3 in eliciting a favorable antibody response.6 There also is evidence that even a single dose of the vaccine can elicit a protective immune response.7 This encouraging finding is particularly important to public health officials responsible for developing HPV vaccination programs in low- and middle-resource countries.
Continue to: Target groups for the HPV vaccine...