Merck & Co has been encouraged by new data from the US Centers for Disease Control and Prevention which seems to suggest that its RotaTeq vaccine may have contributed to a reduced incidence of rotavirus infection during the current season.

The agency’s interim report on the 2007-2008 season indicates that rotavirus activity began in February, three months later than the previous 15 years, but it reveals that the number of tests requested for the virus between January 1 and May 3 was 37% lower than normal. Those testing positive fell by 79%.

Moreover, the CDC study indicates that the changes may have resulted from the introduction of RotaTeq in 2006. Anne Schuchat, director of the CDC’s National Center for Immunization and Respiratory Diseases, said the changes observed were "greater than expected based on the protective effects of the vaccine alone," adding that “it is also possible that current levels of vaccination may be helping to decrease the spread of rotavirus to unvaccinated individuals in the community".

However Merck's plans to expand the use of its human papillomavirus jab Gardasil have received a setback. The US Food and Drug Administration has responded to the firm's request to approve the vaccine for women between 27 and 45 by highlighting “issues that preclude approval within the expected review timeframe”.

Merck provided very few details regarding its correspondence with the FDA and lmited itself to saying that it has already discussed with the agency the questions related to the application and expects to respond in July. Gardasil was approved in 2006 for girls and women between 9 and 26 years old to prevent HPV, which can lead to cervical cancer.

The company did note that the FDA has stated that the data submitted do not support extending Gardasil’s use to include non-vaccine HPV types (cross protection). Commenting on the bid to get expanded approval for Gardasil in older women, Barbara Ryan of Deutsche Bank said in a research note that it appears Merck has the data in hand "to adequately address the concerns, which likely centre around efficacy rather than safety considerations. Nevertheless, the timing of the complete response and the subsequent additional review period remain unclear".

She added that the age extension indication is seen as "an incremental commercial opportunity, but one where we would also expect a much lower penetration rate". Merck has previously indicated that use for males, "which we believe is the most important incremental opportunity for Gardasil," will be filed later this year.