GlaxoSmithKline’s cervical cancer vaccine Cervarix seems to be as effective in older women aged 26 to 55 as it is in younger females, according to clinical data presented at the American Society of Clinical Oncology annual meeting.

The results back up earlier clinical trials showing 100% protection with Cervarix for up to 4.5 years in younger women aged 15 to 25 – which were used to support a marketing application for Cervarix in Europe – and are important because around 5% of new infections with human papillomavirus – the virus that predisposes women to develop cervical cancer - occur in older women.

In this Phase III study, 100% of women across all studied age groups demonstrated antibody response one month after completion of the vaccination course against HPV types 16 and 18, the two most common cancer-causing forms of the virus. Philippe Monteyne, head of global vaccine development at GSK Biologicals in Belgium, said there was also evidence that Cervarix provided crossover protection against other HPV strains, including 45 and 31 which are the third and fourth most prevalent cancer-causing strains.

The data will be incorporated into GSK’s license application for Cervarix, due to be filed in the USA later this year, and could help the company in its marketing battle with rivals Merck & Co and Sanofi Pasteur MSD, which have submitted for approval of a competing vaccine, Gardasil.

Analysts at Collins Stewart said last month they expect Cervarix to win the lion’s share of the market for HPV vaccination, suggesting that the immune response to GSK’s vaccine is so potent that one shot could confer 15 years of protection, while Gardasil may require regular boosters. They product peak sales of $5.5 billion for Cervarix.

Meanwhile, Merck was blowing the trumpet for Gardasil at the ASCO meeting as well, presenting new data showing that Gardasil can also inhibit the development of two other tumour types – vulvar and vaginal cancer – that together affect around 6,000 women in the USA each year.

HPV is found in more than three quarters of vulvar cancers and about two third of vaginal cancers.