This is a welcome shot in the arm for the drugmaker, which earlier today noted that the FDA declined to approve - at least for now - the use of its Gardasil HPV vaccine in most women. Now, though, Merck is crowing that its Rotateq vaccine delayed the onset of the rotavirus season by about three months - from November to February - compared with the start time for the previous 15 years. Here is the CDC report.

The vaccine was recommended two years ago for routine immunization of infants at 2, 4 and 6 months of age. Rotavirus, by the way, is the leading cause of severe gastroenteritis, which involves vomiting and diarrhea, and causes more than 200,000 US children to require emergency care each year. Up to 60 children die from the bug in the US and about 1,600 globally on an annual basis.

The results mark a significant turnabout in care, since an earlier vaccine from Wyeth was pulled from the market in 1999 after being linked to a rare and fatal bowel obstruction. Since Rotateq became available, the number of lab tests for the virus from January to May 2008, was 37 percent lower than usual, and those testing positive fell by 79 percent.

“The changes appear to be greater than expected based on the protective effects of the vaccine alone,” Anne Schuchat, director of the National Center for Immunization and Respiratory Diseases at CDC, says in a statement. “It is also possible that current levels of vaccination may be helping to decrease the spread of rotavirus to unvaccinated individuals in the community.”

Here is the Merck statement.