A new study has found that the current estimates of Human Papillomavirus (HPV) infection rates in girls and women in the US are too low. It suggests the actual infection rate is about 60 per cent higher, or about 1 in 4 females aged between 14 and 59. This is equivalent to 25 million American girls and women.
The study is published in today’s issue of the Journal of the American Medical Association.
Dr Eileen F. Dunne of the Centers for Disease Control and Prevention (CDC) in Atlanta and her research team wanted to establish a baseline figure for the prevalence of HPVs in American women before the vaccine programme that is currently being planned by many states becomes widespread.
HPVs are the most common sexually transmitted infections in the US and are also linked to cervical cancer. There are over 100 types of HPV, of which the high risk ones are thought to cause cervical, anal and other cancers. 99 per cent of cervical cancer cases are accompanied by high risk HPVs.
Women tend to become infected with HPVs just after becoming sexually active, and for 90 per cent of them the infection clears of its own accord within 2 years.
The Food and Drug Administration in the US has approved Gardasil (made by Merck), a very effective vaccine against certain high risk HPVs and recommended that all girls aged 11 and 12 be vaccinated with it.
Gardasil protects against two HPV types (16 and 18) that cause about 70 per cent of cervical cancers. It also protects against two other HPVs that are not linked to cancer. These are types 6 and 11 and cause nearly 90 per cent of genital wart infections.
In this study Dunne and her colleagues used nationwide data from about 2,000 women and girls taking part in the the National Health and Nutrition Examination Survey (NHANES) during 2003 and 2004.
The information comes from home-based interviews, to collect data on demographic and sexual behaviour, and mobile examination units, where self-collected vaginal swabs were sampled and tested later for HPV DNA.
The results showed that the overall prevalence of HPV was 27 per cent for all females aged from 14 to 59. Within this, the figures for each female age group was about 1 in 4 for teenage girls, rising rapidly to nearly half of those in their early twenties, and then going down to about 1 in 5 in females in their fifties.
More specifically the figures for female HPV prevalence found by the study are:
– 25 per cent for 14 to 19,
– 45 per cent for 20 to 24,
– 27 per cent for 25 to 29,
– 28 per cent for 30 to 39,
– 25 per cent for 40 to 49,
– 20 per cent for 50 to 59 years of age.
Apart from age, other independent risk factors for HPV detection were marital status and rise in numbers of lifetime and recent sex partners.
The analysis also checked the prevalence of different forms of HPV, including the types that are covered by the impending vaccination programmes.
This showed that the types of HPV that are covered by the vaccine were present in 3.4 per cent of the females in the survey.
Dunne and colleagues concluded that HPV is common in the US female population and that it is more prevalent than current estimates would have it, with the highest infection rates being in the 20 to 24 age group.
They said “Our study provides the first national estimate of prevalent HPV infection among females aged 14 to 59 years.”
However, the rate of infection of HPVs covered by the new vaccine is low compared to the overall HPV infection rate.
“Prevalence of HPV Infection Among Females in the United States.”
Eileen F. Dunne, Elizabeth R. Unger, Maya Sternberg, Geraldine McQuillan, PDavid C. Swan, Sonya S. Patel, Lauri E. Markowitz.
Vol. 297 No. 8, February 28, 2007.
Written by: Catharine Paddock
Writer: Medical News Today