Some cancers can be caused by viral infections. Cervical cancer is one such cancer. The human papillomavirus (HPV) is the virus responsible for cervical cancer. Some women who have had HPV can go on to develop cervical cancer.

There are over 100 types of HPV, and more than 40 of these are known to infect the genital skin of both men and women. Of these 40 types, some cause genital warts and others do not, and infection with other types in women can lead to changes in cells of the cervix. These cervical cell changes can, over many years, result in pre-cancerous cell types. These are the cells that cervical screening programmes (smear tests) aim to detect, allowing women to get treatment before the cells become cancerous.

HPV is the most common sexually transmitted infection. Studies of women have found three out of four sexually active women (75%) have been or will be infected with HPV during their lifetime. One US study has estimated that about half of all sexually active young men and women will acquire an HPV infection within five years of first having sexual intercourse. The rates of genital HPV infection are thought to be directly related to sexual activity. The particular risk for any individual is linked to the number of sexual partners.

HPV infections are usually cleared from the body (over approximately 12-30 months) without further problems, but if not cleared, some progress to cervical and other female genital cancers, and to anal cancers and genital warts in both men and women.

Prevention of HPV infection

Safe sexual behaviour will reduce the risk of sexually transmitted infections in general (see our Sexual Health centre for more information). If you do not have a regular long-term sexual partner, you or your partner should always use a condom when having sex, to prevent a number of possible infections. HPV is a very common virus, and studies show that condom use offers only partial protection against it.

A newly available vaccine (Gardasil) is highly effective against the four most important types of HPV (types 6, 11, 16 and 18). HPV types 16 and 18 cause about 70% of high-grade pre-cancerous changes and cervical cancers. HPV types 6 and 11 cause some low-grade pre-cancerous changes and 90% of genital warts.

The vaccine prevents future infection, it does not cure an existing infection. However, even if you have been sexually active, and have already been infected with one HPV type contained in the vaccine, the vaccine still provides 100% protection against the other three types in the vaccine. The vaccine may also reduce the likelihood that the existing HPV infection progresses to a pre-cancerous change, although this is still being studied.

A second HPV vaccine has recently been registered for use in New Zealand (Cervarix - which offers protection against HPV types 16 and 18). Both vaccines have been extensively studied and have shown excellent safety.

It should be remembered these HPV virus types are responsible for most, but not all, of the HPV types that can lead to cervical cancer. So routine cervical screening will still be recommended. Also, screening is necessary because of the possible effects of persistent HPV infection that may have occured before vaccination.

Studies are ongoing to determine the likely length of vaccine protection and the need for booster shots in later years, although four or five years protection has been observed so far.

Quick facts about human papillomavirus (HPV)

• HPV is the most common sexually transmitted infection (STI) worldwide
• Up to three-quarters of sexually active adults will be infected with HPV during their lifetime
• The majority of HPV infections occur without any symptoms, so you do not know you have an infection
• Most HPV infections are cleared by the immune system within 12-30 months
• Long term HPV infection can cause changes to the cells of the cervix, cervical cancer (taking up to 20 years) or genital warts
• The types of HPV that cause cervical cancer are different from the types that cause genital warts
• Over 99% of cervical cancers are caused by HPV infection
• Condom use does not fully protect against HPV, but condom use is still recommended to protect against other STIs.

Quick facts about the HPV vaccine (Gardasil)

• The vaccine prevents infection, it does not cure existing infection, so it is most useful if given before sexual activity begins
• The vaccine is indicated for girls and young women aged 9-26 years and males 9-15 years
• The vaccine offers 100% protection against the main types of human papillomavirus (HPV 6, 11, 16 and 18)
• These types account for about 70% of cervical cancers and high-grade pre-cancers and 90% of genital warts
• If you have been infected with one HPV type, the vaccine still protects you against the other types contained in the vaccine
• There is no routinely available test to detect current or previous infection with HPV
• The vaccine is given in three doses over a six-month period (0, 2 and 6 months).

Funding for Gardasil vaccine

The HPV vaccine (Gardasil) is funded by the New Zealand Government for certain age groups. Those eligible for funded vaccination:

From 1 September 2008
Girls aged 17 and 18 years (born in 1990 and 1991) are able to receive HPV vaccine from primary care or health clinics.

From 2009
-HPV vaccine will be part of the National Immunisation Schedule for 12-year-old girls (in primary care and health clinics) and girls in school Year 8. 
-HPV vaccine will be offered to girls aged 13 to 18 years. This will be phased in over 2009 and 2010.

Smoking also a risk factor

As cervical cancer is the second most common cause of cancer death in women on a worldwide basis, the HPV vaccine represents a significant advance in preventive health. It is also important to remember that smoking is related to increased development of abnormal cells in the cervix, so by quitting smoking you remove an additional important risk factor.

For women who discover they have early pre-cancerous changes to the cells of the cervix, there are some commonly used surgical procedures that can prevent progression to cervical cancer. These include colposcopy, cone biopsy and loop electrosurgical excision procedure (LEEP).

HPV vaccine - Frequently Asked Questions

Original material provided by everybody, reviewed December 2008.