Trials on a vaccine for cervical cancer have shown it protects women for up to four and a half years, according to research published today.

Scientists have been work-ing on vaccines for cervical cancer for years but the new research assesses the long term impact.

Cervical cancer kills more than 1,000 women in the UK every year and its main cause is persistent infection with the human papilloma virus (HPV) virus.

Some forms of the HPV virus only cause genital warts, but others cause cervical cancer.

Up to half of the young women in the UK are thought to have been infected with a high-risk strain of HPV by the time they are 30.

The new research, published online today by The Lancet, involved studying a vaccine for the common types of HPV associated with the disease, HPV-16 and HPV-18.

Dr Diane Harper, of the Dartmouth Medical School in Hanover, New Hampshire, US, and her team conducted follow-up tests using smear test samples on 800 women who took part in a 2004 trial of the vaccine.

The women had either received three doses of the HPV-16/HPV-18 vaccine or a dummy pill.

The researchers found that women given the vaccine had high levels of antibodies against HPV-16 and HPV-18 for up to four and a half years after receiving the last dose.

The vaccine was effective against persistent and new infections and also protected against infection with HPV-45 and HPV-31 - the third and fourth most common types of HPV.

Dr Harper said the study showed the vaccine to be safe in the long term and that it provided "substantial" long-term protection against cancerous cell changes associated with HPV.

She added: "These findings set the stage for the widescale adoption of HPV vaccination for prevention of cervical cancer."

Between 2004 and 2005, 3.6 million women in England underwent cervical screening and 12,071 women were diagnosed with some degree of cell abnormality, according to the N HS Cancer Screening Programmes.

A survey from pharmaceutical giant GlaxoSmithKline, released today, found just one in 25 British women was aware that HPV leads to cervical cancer.

Although a quarter of the 978 women (26 per cent) questioned had heard of the virus, only four per cent knew it was the main cause of cervical cancer.

Almost a third (31 per cent) of women said they did not know the cause of the cancer, while 36 per cent said it was related to "sexual practices".

A fifth (20 per cent) thought it was down to hereditary or genetic factors, 18 per cent said lifestyle factors and 16 per cent said infections.

Other research, unveiled at the European Congress of Obstetrics and Gynaecology in Turin, found that just one in 20 women across Europe were able to identify HPV as a major cause of the cancer.

In the EU, around 32,748 women are diagnosed with cervical cancer every year, and 14,401 die from it. ..SUPL: