With some of its best-selling drugs falling off the patient cliff, and big employee cuts looming in France, Sanofi ($SNY) is looking for improved sales elsewhere--like from its vaccine division. One of its most promising vaccines, with sales estimated to push beyond $1 billion, is a treatment for four strains of the deadly dengue fever. But it got the chair knocked out from under it on that one this week when it reported the vaccine failed to protect against a strain common in Thailand. Success with the study could have set Sanofi up for regulatory approval but now it must wait for results of two trials in Asia and Latin America. Story | More