INFECTIOUS DISEASE

Vaccinated women avoided CIN

Of the 750 women who received placebo, 6 developed HPV-16–related CIN 2, and 6 developed CIN 3. Among the 755 vaccinated women, no cases of CIN occurred. Thus, the vaccine was 100% effective in this trial (95% CI 65–100%).

Among women who received placebo, 111 cases of persistent HPV-16 infection occurred, compared with 7 cases in vaccinated women (vaccine efficacy 94%; 95% CI 88–98%).

Following immunization, antibody to HPV-16 peaked at month 7, declined through month 18, and remained stable between months 30 and 48.

Any effective vaccine is important

Because 3,500 to 4,000 women still die from cervical cancer each year in the United States, and almost 274,000 die worldwide, the development of any HPV vaccine that provides lasting protection against CIN is important.

The vaccine evaluated by Mao and colleagues targeted a single strain of HPV, genotype 16. The recently approved quadrivalent vaccine, Gardasil, targets types 6, 11, 16, and 18. Of the more than 100 genotypes of HPV that have been discovered, approximately 30 are present in the mucosa of the genital tract, and 15 of these 30 are associated with cervical cancer. However, 2 HPV strains—types 16 and 18—are responsible for about two thirds of all cases of cervical cancer; 90% of genital warts cases result from infection with types 6 and 11.¹⁰

Emphasize to patients that preexisting cytologic abnormalities and genital warts don’t respond to vaccination against human papillomavirus.The Advisory Committee on Immunization Practices recommends that the quadrivalent vaccine be given to girls at age 11 or 12 years, prior to the onset of sexual activity, to be maximally effective against all 4 genotypes included in the vaccine.¹⁰

If a woman is infected with HPV prior to vaccination, she may develop abnormal cervical cytology related to the genotypes in the vaccine, as well as genotypes not included. Nevertheless, ACOG recommends that the vaccine be considered in all females ages 9 to 26.¹¹ HPV genotyping is not recommended before giving the vaccine because any type of routine screening reduces the cost-effectiveness of the vaccination program.¹⁰

Fundamentals of vaccination

The quadrivalent vaccine must be administered intramuscularly (0.5 mL) in 3 doses on day 1 and at 2 and 6 months. The principal adverse effect is a local reaction such as pain, swelling, or pruritus at the injection site. Low-grade fever occurs in approximately 10% of patients.

Although the vaccine is classified by the FDA as pregnancy category B, the manufacturer recommends against its use during pregnancy. It may be administered to lactating women, however. The approximate cost of the 3-dose series, including administration fees, is $400 to $500.

It’s a vaccine, not a treatment

Patients need to understand that vaccination is not a treatment for preexisting cytologic abnormalities or genital warts. Nor can it be expected to be perfectly protective over a person’s lifetime against infection caused by genotypes 6, 11, 16, and 18. Women must continue to have regular cytologic screening. No reliable scientific data suggest that vaccination of young girls will increase sexual promiscuity in the adolescent population.¹⁰

The author reports no financial relationships relevant to this article.