Přináší HPV vakcína benefit i ženám již HPV nakaženým? (angl.)

The HPV vaccine does not eradicate infection that is already present, but may still provide some benefit to women who already are infected with HPV.

Human papilloma virus (HPV) has over 100 genotypes. Of the 30 identified genital HPV types, at least 11 are known, in some cases, to lead to cervical cancer. About 70% of these cancers are caused by types 16 and 18. These same high-risk types of HPV can also cause a proportion of anal, vulvar, vaginal, and penile cancers. Less virulent forms of HPV (types 6 and 11) are associated with low-grade cervical abnormalities and 90% of genital warts.[1]

The FDA-approved quadrivalent vaccine for the prevention of HPV (Gardasil) protects against 4 HPV types (6, 11, 16, 18). The vaccine was tested with a 5-year follow-up in over 11,000 females ages 9-26 years. Gardasil proved to be highly effective in preventing cervical, vulvar, and vaginal precancers as well as genital warts caused by the HPV types targeted by the vaccine. There is no information regarding efficacy of the vaccine beyond 5 years, although follow-up is ongoing.

The Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices (ACIP) recommends routine vaccination with HPV vaccine in a series of 3 doses for all females 11-12 years of age and catch-up vaccination for females 13-26 years of age who have not been vaccinated previously.[2] This series can begin at age 9 years, when exposure to sexually acquired HPV would be least likely. In addition, clinical trials demonstrated that titers were highest among those participants who were vaccinated at earlier ages.[3] No serious adverse effects have been documented.

Mild reactions involve local injection-site reactions or pain. There are no recommendations for precautions other than those taken during routine childhood vaccinations. However, given that this vaccine is new, there is still a need to be vigilant for extremely rare adverse reactions. The Vaccine Adverse Event Reporting System (VAERS) is a joint FDA/CDC program for providers to report any adverse reactions.[4]

It is important to remember that 30% of cervical cancers are caused by HPV types not prevented by the quadrivalent HPV vaccine.[1] The current vaccine will only protect against the 4 HPV types that it targets. A female may be vaccinated according to the current guidelines and still become infected with an HPV type that is not targeted by Gardasil. Therefore, cervical Pap smear screening guidelines are the same, regardless of whether a woman is vaccinated or not. Lack of screening is a major contributing factor to cervical cancer mortality.

Another issue is the possibility that a young woman may have been infected with HPV prior to being vaccinated. None of the women in the clinical trials tested positive for HPV when initially enrolled, but in a real-world scenario, the possibility of prior infection exists. Most women will clear the infection within 6 months to 2 years, but there is still a great deal that is unknown about the natural history of HPV. This clearance may indicate that the infection is gone or that it is undetectable — in a more latent phase. At the present time, it isn't possible to determine whether a woman has been infected with specific types of HPV because laboratory results are only available as "high risk" or "low risk."

The ACIP states, "Quadrivalent HPV vaccine can be given to females who have an equivocal or abnormal Pap test, a positive Hybrid Capture II high risk test or genital warts. Vaccine recipients should be advised that data from clinical trials do not indicate that the vaccine will have any therapeutic effect on existing Pap test abnormalities, HPV infection, or genital warts. Vaccination of these females would provide protection against infection with vaccine HPV types not already acquired."[2]

The HPV vaccine does not completely eliminate cervical cancer risk. However, when given to females not previously infected with HPV types 6, 11, 16, or 18, it is highly effective in preventing infection. Ongoing studies will certainly add to our knowledge of cervical cancer prevention as well as the natural history of HPV.

Zdroj: Medscape