A vaccine shown to be 100% effective against two virus strains that cause most cervical cancer could be available within a year, say manufacturers.

Gardasil worked against the sexually transmitted human papillomavirus (HPV).

Some 12,167 women aged 16 to 23 from 13 countries, including the UK, took part in the drug company study.

Researchers believe a vaccine could work best if given before adolescence, but critics fear this could encourage under-age sex.

Merck’s vaccine is in head-to-head competition with a rival from UK-based GlaxoSmithKline called Cervarix.

Cervical cancer kills 274,000 women worldwide every year, including 1,120 in the UK.

The two-year Future II trial found Gardasil was 100% effective at preventing early stage cancers and pre-cancerous abnormalities caused by the two key strains of HPV – the 16 and 18 strains – which cause 70% of cervical cancers.

Julietta Patnick, director of the NHS Cancer Screening Programmes, said regular cervical screening was the best way of preventing cervical cancer.

All women registered with a GP should receive their first invitation at 25 and then every three years until they are 49. Women between 50 and 64 will be invited every five years.