Sexually active college-age women have a high incidence of human papillomavirus (HPV) infection according to a study supported by the National Institute of Allergy and Infectious Disease (NIAID) and reported in the Feb. 12, 1998 issue of The New England Journal of Medicine.
"Genital infection with HPV is one of the most common sexually transmitted diseases, with its prevalence in young women ranging from 20 percent to 46 percent in different countries," says Study Director Robert D. Burk, M.D., of the Department of Pediatrics, Microbiology and Immunology, and the Department of Epidemiology and Social Medicine at the Albert Einstein College of Medicine. "The public health impact of this infection is compounded by the recognized causal relationship between genital infections with certain types of HPV and cell abnormalities of the cervix and cervical cancer."
"The incidence of HPV infection in sexually active young college women is alarming. Furthermore, we currently have no effective way to prevent infection. The need for topical microbicides and effective vaccines is urgent," says Penny Hitchcock, D.V.M., chief of the sexually transmitted diseases branch in NIAID's Division of Microbiology and Infectious Diseases. "It is certainly reassuring that only a small number of women will develop cervical cell changes or cancer. However, until we have more precise diagnostic tests, it is important for young women to have regular Pap smears."
Through campus-wide advertisements at a state university in New Brunswick, N.J., the study team enrolled 608 young women. Their average age was 20 years, and the ethnic distribution was 57 percent white, 13 percent Hispanic, 12 percent black and 18 percent other. Twenty-six percent were diagnosed with HPV infection at the beginning of the study. Each of the women had pelvic examinations and Pap smears at the study outset and annually. For a maximum of three years, the women responded at six-month intervals to questionnaires on lifestyle and sexual behavior. At the same visits, samples of cells from the cervix and vagina were taken to ascertain whether or not HPV was present and to determine the type, or strain, of HPV. If the same type of HPV was present during two consecutive visits, the infection was defined as persistent. The average duration of HPV infection was eight months.
The cumulative incidence of HPV infection in the women who were HPV-negative at baseline was 43 percent. The investigators noted, however, that this incidence decreased with time: it was 20 percent in the first 12 months; 14 percent in the second 12 months; and only 9 percent in the final 12 months.
"The encouraging news," says Dr. Hitchcock, "is that this study suggests that the body's response to infection plays an important role in limiting persistence of the virus and disease progression. If this is mediated by the immune response, it could indicate that development of prophylactic and therapeutic vaccines would play an important role in prevention and control."
Higher risk and incidence of HPV infection are associated with younger age, ethnic minority subgroups, increased frequency of alcohol consumption, anal sex or a high frequency of vaginal sex. A woman was less likely to have an HPV infection last for six months if it had been her first infection. The longer an infection endured from previous visits, the more likely it was to persist.
One of the consequences of HPV infection is the presence of various types of abnormal cells. One such type, squamous intraepithelial lesion, a potentially pre-cancerous condition, is caused by HPV infection of cervical cells, and is usually first detected as an abnormal Pap smear.
The authors caution that because of the six-month interval between medical visits, the study results may underestimate the incidence and overestimate the duration of HPV infection. They also warn that it is uncertain whether these data apply to older women.
In addition to Dr. Burk, collaborators included Gloria Y. F. Yo, Ph.D., and Chee J. Chang, Ph.D., both of the Albert Einstein College of Medicine, Bronx, N.Y.; and Robert Bierman, M.D., and Leah Beardsley, N.P., both of Rutgers University Student Health Service, New Brunswick, N.J.
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