New Examination of HPV Prevalence in US Women
Abstract & Commentary
By Robert L. Coleman, MD, Associate Professor, University of Texas; M.D. Anderson Cancer Center, Houston, is Associate Editor for OB/GYN Clinical Alert.
Dr. Coleman reports no financial relationship to this field of study.
Synopsis: Vigorously conducted study of HPV infection demonstrates prevalence is higher than previously estimated.
Source: Dunne ER, et al. Prevalence of HPV infection among females in the United States. JAMA. 2007;297:813-819.
Human Papilloma Virus (HPV) infection is the most common sexually transmitted disease in US women. Its prevalence rises sharply after sexual debut and peaks between ages 20 and 29; prevalence is lower in older women. Since more than 99% of cervix cancer patients have evidence of HPV infection, clear understanding of the health care burden is necessary, particularly in light of the recent availability of the HPV vaccine. Using data obtained from a recent survey of women participating in the National Health and Nutrition Examination Survey (NHANES), Dunne and her colleagues examined the prevalence of HPV infection in this large cohort. Participants were women who were surveyed in 2003 and 2004 and had their HPV infection status determined by standard methodology from self-collected vaginal swabs. Both high- and low- risk HPV subtypes were evaluated (n = 38 total) in the study cohort of 1921 evaluable women aged 14-59. Over all age cohorts, HPV was identified in 26.8% of women. This corresponds to an estimated 24.9 million women in this age group in the US population. Prevalence was highest in women aged 20-24 years (44.8% or 7.5 million individuals). There was a significant trend in prevalence with each year from 14 to 24 years of age followed by a gradual decline in prevalence through age 59. HPV 6, 11 and 16, 18 (targets of the current quadravalent HPV vaccine) was detected in 3.4% of the participants. Overall, 40% of women had more than one HPV type infection. The authors conclude HPV prevalence is high in the US population, particularly in women aged 20-24. However, the prevalence of HPV subtypes included in the current HPV vaccine is low.
It has been widely known that HPV is prevalent in the US population. Fortunately, despite this finding, the incidence of cervix cancer is low owing to broad acceptance of Pap smear testing and effective treatment of slow growing preinvasive lesions. However, the impact of HPV infection in the setting of underdeveloped preventative care is prominently represented; worldwide, cervix cancer is among the most frequent causes of cancer death in women. These observations are driving impetus for both prevention and screening programs throughout the world for this largely preventable killer. In the US, a quadravalent HPV vaccine (HPV types 6, 11, 16, 18) is approved and has been demonstrated to be nearly 100% effective in preventing infection and disease associated with these subtypes and is currently approved for routine use. Two interesting facts are highlighted in the current study: first, the prevalence of infection is much higher than previously documented. In this cross-sectional determination, over one quarter of the participants tested positive and the prevalence among 20-24 year olds has increased over serial studies. However, the prevalence in 14-19 year olds was also nearly 25%, suggesting effective intervention strategies have to start in younger girls. In fact, only this age group was associated with a significantly increased ratio of high risk to low risk HPV subtype infection. The second important observation in the trial was the high prevalence of HPV types, which are not currently a target of the HPV vaccine. Just 3% of infected individuals had these subtypes. Other studies, predominantly from clinic-based populations, have demonstrated a much higher contribution of these serotypes and their high frequency in cancer specimens has directed the current vaccine portfolio. It is possible that these more prevalent serotypes have shorter infection cycles and less significant clinical implications. It is also possible that certain HPV types have a tropism for the vagina, as opposed to the cervix. However, a concern of vaccination programs is that over time there could be a "serotype-shift" or selection to other cancer-inducing HPV serotypes. Indeed, the most prevalent high-risk HPV serotype identified in this study was HPV-53; this serotype is identified in less than 1% of cancer currently. The impact of these observations will likely direct future vaccine development as the portfolio expands.
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