Pakistani Study Finds High Abortion Rate and Low Level of Contraceptive Use

Abstract

The bivalent human papillomavirus (HPV) vaccine, which generates immunity to the cancer-causing types 16 and 18 of the virus, appears to be effective in protecting women older than 25 against infection and precancerous cervical lesions, according to a randomized trial conducted in 12 countries, including several developing nations. (1) An interim analysis from the trial found that women with no history of HPV infection or disease who received all three doses of the vaccine had an 81% reduction in the risk of six-month persistent infection or precancerous cervical changes associated with HPV 16 or 18, compared with similar women in a control group who received a placebo. (1) Furthermore, the vaccine protected against persistent infection with two other cancer-causing HPV types to which it was not designed to generate immunity. About one in 10 women in both the overall vaccine group and the control group reported a serious adverse event, but very few were related to the vaccine. Although licensed in some countries for use among older individuals, HPV vaccines are generally aimed at teenagers and young adults. To examine vaccine efficacy among older women, the trial, known as the VIVIANE study, enrolled healthy nonpregnant, non-breast-feeding women older than 25 from Australia, Canada, Mexico, the Netherlands, Peru, Philippines, Portugal, Russia, Singapore, Thailand, the United Kingdom and the United States between 2006 and 2010. Enrollment in the seven-year trial was age-stratified such that approximately 45% of women were aged 26-35, 45% were aged 36-45 and 10% were 46 or older. To explore the vaccine's effects among women previously exposed to the virus and to mirror real-world conditions, the study design specified that up to 15% of women in each age-group could have a history of HPV infection or disease, defined as having had two or more abnormal Pap smears in a row, an abnormal colposcopy, or cervical biopsy or treatment after an abnormal smear or colposcopy. Participants were randomly assigned to receive the bivalent HPV vaccine (marketed as Cervarix) or a control vaccine on a double-blind basis. Cervical samples were collected for HPV DNA testing every six months and Pap testing every 12 months, and blood samples were collected every 6-12 months to assess levels of HPV antibodies. The interim analysis was performed after all women had completed the 48-month visit. For each group, the investigators computed the rate of HPV 16 or 18 infection lasting at least six months or of precancerous cervical changes (cervical intraepithelial neoplasia of grade 1 or higher, CIN1+); they calculated vaccine efficacy as 1 minus the rate ratio (the rate of events in the HPV vaccine group divided by the rate in the control group). During the trial, 5,752 women received at least one dose of HPV vaccine or placebo and were included in the total vaccinated cohort; on average, women were 37 years old. At baseline, about one-third in each group tested positive for HPV 16 and a similar proportion for HPV 18; one-fourth had had six or more lifetime sexual partners. Main efficacy analyses were based on the 4,505 women who received all three planned doses of vaccine or placebo, had normal or low-grade cervical cytology at baseline and had no history of HPV infection or disease; the mean duration of follow-up in this cohort was 40 months. …