HPV vaccines could prevent most cervical cancers
By Will Boggs MD
NEW YORK (Reuters Health) - The available human papillomavirus (HPV) vaccines could prevent most cases of cervical intraepithelial neoplasia (CIN) and adenocarcinoma in situ, according to an HPV genotype study.
"The estimate of prevention of 90% of invasive cervical cancers is based on epidemiologic studies which show the nine HPV types included in the vaccine are present in 90% of HPV-related cervical cancers," Dr. Elmar A. Joura from Medical University of Vienna, Austria told Reuters Health by email.
"Yes, the vaccine would have to be highly effective in preventing infection and disease associated with these types," Dr. Joura continued. "In Phase III studies, the 9-valent vaccine prevented approximately 97 percent of high-grade cervical, vulvar, and vaginal diseases caused by the five additional HPV types."
The current 9-valent HPV vaccine types include the high-risk types HPV16/18/31/33/45/52/58 along with HPV6/11 (associated with genital warts).
Dr. Joura and colleagues from several other nations used four mathematical approaches to estimate the attributable fraction of high-risk HPV vaccine types in cervical disease, in 10,656 women enrolled in the placebo arms of three phase III trials.
The overall cumulative incidence of any infection with at least one of the high-risk types contained in the 9-valent HPV vaccine was 42% for women ages 15 to 26, 20% for women ages 24 to 34, and 14% for women ages 35 to 45.
The cumulative incidences of persistent infection with at least one of these types were 29%, 12%, and 6% in the three age groups, respectively.
Depending on the mathematical model used, at least one of the seven high-risk HPV types included in the vaccine were present in 43% to 55% of CIN1 samples, 70% to 78% of CIN2 samples, 85% to 91% of CIN3 samples, and 95% to 100% of adenocarcinoma in situ samples, according to a report this month in Cancer Epidemiology, Biomarkers & Prevention.
"This study showed that approximately 85% or more of precancerous lesions of the cervix were attributed to the nine HPV types covered in the vaccine," Dr. Joura said. "Preventing these lesions does not only prevent invasive cancer, it also prevents surgery of the cervix (loop electrosurgical excision procedures) which has been shown to increase the risk for preterm (complications) and neonatal mortality. If 9-valent HPV vaccination programs are effectively implemented, the majority of these lesions could be prevented."
"Despite the clear safety profile of the currently disseminated HPV vaccines, uptake in the United States and other resource-rich countries has been inadequate," Dr. Joura said. "To achieve the population level potential of the HPV vaccine to reduce cancer, vaccine uptake must increase."
A recent CDC review cited by Dr. Joura "found that for health care professionals, concerns about safety were rarely identified as a barrier to vaccination; however, concerns about vaccine adverse effects, safety, and newness were a key barrier to vaccination for parents. To address this, several resources have been developed by CDC including a dedicated website for health care professionals on HPV vaccine resources (http://www.cdc.gov/vaccines/youarethekey). "
Dr. Suzanne M. Garland from Royal Women's Hospital and University of Melbourne, Parkville, Australia told Reuters Health, "The next generation of vaccines (nonavalent) have the capacity to reduce the bulk of cervical cancers and HPV-related diseases. The bulk of disease is in resource poor countries so we really need to focus vaccines to young people there, particularly young girls before sexual debut."
As for improving the uptake of HPV vaccines in the US and elsewhere, she said, "trust that the prophylactic vaccines are definitely safe and (provide) ready access to vaccination: school based programs work particularly well."
Cancer Epidemiol Biomarkers Prev 2014;23:1997-2008.
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