Ananova:

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

Scientists have been working 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."