GlaxoSmithKline is buoyant on the back of new data from the largest cervical cancer vaccine trial to date which shows that Cervarix has proved to be up to 100% effective in preventing precancerous lesions due to the most common types of human papillomavirus, types 16 and 18.

The results, which are published today in The Lancet, come from a Phase III study involving 18,644 women aged 15 to 25 and show that Cervarix was 90.4% effective against types 16 and 18, based on pre-specified analyses that only required detection of virus in the lesion. However, when considering the virus type present in both the lesion and previous samples, the vaccine was proved to be 100%. Cervarix also provided significant cross-protection against infection caused by virus types 45, 31 and 52, which together with 16 and 18, account for more than 80% of cervical cancer cases.

“These results suggest protection from persistent infection with additional cancer-causing virus types beyond those contained in the vaccine,” said Margaret Stanley from the University of Cambridge, adding that “this is important because persistent infection is a necessary first step in the development of precancerous lesions and cervical cancers”.

The data confirms previous data on Cervarix, which is poised to provide a rival to Merck & Co’s Gardasil. The latter is now well established and while GSK’s jab is expected to be approved in Europe in the second half of this year but not before 2008 in the USA. The market is a lucrative one with a whole host of countries backing HPV vaccination programmes so there is plenty of room for two products.

However a warning note was fired in an accompanying editorial in The Lancet. Jessica Kahn of the University of Cincinnati College of Medicine and Robert Burk of the Albert Einstein College of Medicine in New York, said the results were encouraging but it was still too early to assess efficacy, since cervical cancer can evolve over several decades. They also highlighted increases in adverse reactions among vaccinated women, including injection site symptoms and some general symptoms.