GlaxoSmithKline has published new data on its cervical cancer vaccine Cervarix which the firm says generated a significantly higher immune response than Merck & Co's rival product Gardasil, a claim played down by the latter company.

Results of the head-to-head clinical study, involving 1,106 women aged 18-45 and sponsored by GSK, are being presented at the International Papillomavirus Conference at Malmo, Sweden. The data shows that neutralising antibody levels for Cervarix were more than two times higher than Gardasil for human papillomavirus (HPV) type 16 and over six times higher for HPV 18. The company also noted that for HPV types 16 and 18, Cervarix induced 2.7 times more memory B cells.

Both vaccines were well tolerated, but GSK noted that rates of “solicited symptoms” were higher for Cervarix, with injection site reactions being most common. However, in both groups these symptoms tended to be of short duration.

Thomas Breuer, chief medical officer of GSK Biologicals, said that the presence of neutralising antibodies at the location of the infection, the cervix, “appears to be an important part of vaccine-induced protection against HPV”. He went on to say that the study “offers the first evidence that these two vaccines do not generate the same immune response against HPV types 16 and 18, the two most common cancer-causing virus types”.

However, Bennett Lee, medical director for Gardasil at Sanofi Pasteur MSD, the joint venture between Merck and Sanofi-Aventis that sells the jab in Europe, was not overly-impressed. He told Reuters that “we see no clinical relevance in the results of this study...and we don't see the point of doing such a comparison". He added that “if you want to compare vaccines, you compare clinical efficacy”.

GSK will be hoping that the results of the head-to-head study will help it make up some ground on Gardasil in the cervical cancer market. Last year, sales of the latter jab brought in $1.4 billion for Merck, while Cervarix turnover reached $177 million.

Cervarix is still not available in the USA as it only completed its submission to the Food and Drug Administration in March. To date, it has been approved in 95 countries around the world, including the European Union, Australia, Brazil, South Korea, Mexico and Taiwan, and applications have been submitted in more than 20 other countries.

Back to Malmo and GSK is presenting the final analysis of the Phase III study (HPV-008) showing that Cervarix provided “a high and statistically significant level” of efficacy against pre-cancerous lesions associated with HPV 16 and HPV 18. The company will also present results from a third study show that Cervarix provided high and sustained antibody levels through the 7.3 years of follow-up after vaccination. “This is the longest follow-up reported to date for any licensed HPV vaccine”, GSK concluded.