VACCINATING teenage girls in Scotland is helping protect them from the virus that causes cervical cancer, scientists have confirmed.

Screening has revealed a significant reduction in the prevalence of key types of the human papillomavirus (HPV) which increase the risk of women developing the killer disease.

A national immunisation programme was launched in Scotland in 2008 to protect 12 and 13-year-old girls from HPV. Health Protection ­Scotland (HPS) and the University of Strathclyde worked together to assess the early impact of the immunisation programme on infection.

Dr Kevin Pollock, HPS senior epidemiologist, said: "The preliminary findings are very exciting and demonstrate that the HPV vaccine is associated with a significant reduction of HPV types 16 and 18.

"Furthermore, the vaccine also provides cross-protection against three other high-risk HPV types; 31, 33 and 45. Together, these five HPV types are responsible for at least 80% of cervical cancers in Scotland."

Since its introduction, researchers from HPS and the University of Strathclyde have monitored the impact of the HPV vaccine among women attending for cervical smears at age 20.

They revealed a 54% reduction in the number of women who tested positive for HPV types 16 and 18 in the British Journal of Cancer yesterday. Just in excess of 13% of the 4679 women checked were found to have the strains present despite having received the vaccination.

Dr Pollock explained the sample included patients who had received their HPV vaccine later in their teenage years. This is because it was offered to girls up to the age of 17 when it was first introduced. Some of these girls may have been sexually active and caught HPV before they received the injection. Dr Pollok said the vaccine is not as effective once someone has caught the virus.

It is hoped the percentage of girls protected against the two strains will be even greater in future.