Developing a vaccine for meningitis B was tricky. Even the existing vaccine doesn't protect against all B strains. Josef Muellek/iStockphoto.com hide caption

itoggle caption Josef Muellek/iStockphoto.com

The Ivy League school has begun vaccinating nearly 6,000 students to try to stop an outbreak of type B meningitis in an unusual federal government-endorsed administration of a drug not generally approved for use in the U.S. Mel Evans/AP hide caption

itoggle caption Mel Evans/AP

Princeton University's Nassau Hall. DANIEL HULSHIZER/AP hide caption

itoggle caption DANIEL HULSHIZER/AP