The human papillomavirus (HPV) vaccine Cervarix "offers excellent protection" against serious cell changes that lead to cervical cancer, particularly when given to young adolescent girls before they become sexually active, according to research published in the Lancet Oncology.

A second study published in the same journal showed that Cervarix also protects against several other cancer-causing HPV types that it's not specifically designed to target, giving protection against a group of strains that together cause about 85 percent of cervical cancers worldwide.

Cervical cancer affects around 2,800 women each year in the UK, and is the second most common cancer in women under 35.

Virtually all cases are linked to genital infection with HPV, the most common viral infection of the reproductive tract. In the UK, girls in year 8 at school (aged 12 to 13 years) are offered the Cervarix vaccine.

There are several types of HPV - Cervarix was designed to target HPV types 16 and 18.

Until now, most studies of the vaccine have focussed on whether it protects against precancerous changes called CIN2+ lesions. In this latest analysis, the researchers looked specifically at the effect of the vaccine against the more serious immediate precursors to cervical cancer, called CIN3+ and adenocarcinoma in situ (AIS) lesions.

Almost 20,000 women aged between 15 and 25 from around the world were examined as part of the study, in which participants were given either Cervarix or a control vaccine in three doses during a six-month period.

In young women not already infected with HPV, the vaccine proved over 93 per cent effective against CIN3+ lesions and prevented 100 per cent of AIS lesions.

In the general population, the vaccine was nearly 46 per cent effective against CIN3+ and 77 per cent effective against AIS.

One of the study leaders, Matti Lehtinen, from the University of Tampere in Finland, said: "Provided that organised vaccination programmes achieve high coverage in early adolescents before sexual debut, HPV vaccination has the potential to substantially reduce the incidence of cervical cancer, probably allowing modification of screening programmes... when conducted alongside vaccination strategies."

In the second study, the vaccine was shown to partially protect against HPV types 31, 33, 45, and 51.

Of the results, Cosette Wheeler from the University of New Mexico Health Sciences Center in the US said: "Our results show that cross-protective efficacy might provide substantial additional protection against cervical cancer beyond protection conferred against HPV-16/18".

Jessica Harris, senior health information officer at Cancer Research UK, said: "These two new studies underline the importance of as many 12-13 year old girls as possible taking up HPV vaccination. They clearly show that the vaccine is effective against serious cervical cell changes that have a high chance of progressing into cancer.

"Cervarix also at least partly protects against some other HPV types that aren't the target of the vaccine, which could lead to it preventing even more cancers in future."

Source: CRUK