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The genital human papillomavirus (HPV) is a highly contagious, common and usually symptom free infection.
Many people acquire HPV within a few years of becoming sexually active.
In most cases the HPV infection will clear up within 12-24 months. In a small number of cases though, the virus persists and may lead to cervical cancer.
There are many different strains of HPV. 15 HPV types are high risk types, of which two (HPV 16 and HPV18) are the most common.
High risk types can establish persistent cervical infection in about 3-10% of infected women. This can result in cervical abnormalities that in some cases will progress to cervical cancer.
About 70%-80% of cervical cancers are attributed to HPV types 16 and 18.
High risk types have also been associated with the development of some anal cancers, vaginal and vulval
cancers, penile cancers and head and neck cancers.
In Australia, there are about 750 cases, 1800 hospitalisations and 250 deaths each year from cervical cancer.
Cervical cancer in Australia now occurs mainly in unscreened or underscreened women. In addition, low risk genital HPV types 6 and 11 are important causes of genital warts, causing about 90% of all genital warts.
Vaccination can provide protection against some types of HPV. Currently, Gardasil is the only funded HPV vaccine available.
It is approved for females aged 9 to 26 years. Gardasil provides 90-100% protection against HPV types 16, 18, 6 and 11. A three dose schedule is recommended over six months.
Another HPV vaccine, Cervarix, which will provide protection against HPV types 16 and 18, is also available but not provided free.
Vaccination can be considered for any female aged 9 to 26 before the start of sexual activity. It is not routinely recommended for women who are already sexually active. However, some women may benefit from vaccination, after assessing the likelihood of their past and future exposure to HPV, as the vaccine can still give protection from those HPV types that the woman may have not acquired.
HPV vaccines will not treat existing HPV infection or disease. They are preventive treatment only.
Gardisil is also approved for use in males aged 9 to 15 years. This approval is based on the demonstration of safety and HPV antibody responses in males. However, there is currently no data demonstrating that HPV vaccination of males is effective in preventing HPV infection, genital warts or other genital lesions. This data is expected by the end of 2009 and when more information is available, the vaccine may be recommended for boys as well.
It is not yet known how much protection is given from receiving only one or two doses of the vaccine. For this reason it is very important to have all three doses. The duration of immunity from the vaccination is not yet known. It is at least five years, but booster doses may be required.
Pap smears are an important preventive strategy against cervical cancer.
Since no vaccine is 100% effective and Gardasil does not provide protection against all HPV types, or against existing HPV infections, routine Pap screening for sexually active women remains critically important to detect precancerous changes in the cervix.
This allows treatment before cervical cancer develops.
The vaccine is a ‘recombinant vaccine’ made by genetic engineering, whereby the genetic material of an organism is manipulated. In this case, the genes that code for a specific protein from each of the four HPV virus types are expressed in yeast to create large quantities of the protein. The protein that is produced is purified and then used to make the vaccine. Because the vaccine only contains a protein and not the entire virus, the vaccine cannot cause HPV infection. It is the body’s immune response to the recombinant protein/s that protects against infection by the naturally occurring virus.
A three dose regime will approx cost $390-$450 ($130-$150 per dose) depending on supplier. Gardasil vaccine is currently provided free as part of the annual school based program for year 7 girls. It also is provided free to girls aged 9-26 years from your GP or immunisation provider, but you need to receive your first dose prior to 30 June and complete the remaining doses prior to 31 December, 2009. It is not yet known how much protection you get from receiving only one or two doses of the vaccine; for this reason it is very important that you get all three doses. The duration of immunity from vaccination is not yet known. It is at least five years, but booster doses may be required.
For more information about HPV vaccination, speak to your GP .
Illustrations taken from Understanding Childhood Immunisation, with permission from the Commonwealth Department of Human Service and Health.