MADISON, Wis. — The University of Wisconsin-Madison is urging all undergraduates to get vaccinated against a rare form of meningitis that put two students in the hospital last week.

University Health Services is offering the vaccine free to students starting Thursday. It’s effective against the B strain of the disease. Few students are vaccinated against the strain because the two-dose vaccine is relatively new. Most students have been vaccinated only against four common strains — A, C, Y and W.

The university says the two students who became ill with the B strain are expected to make full recoveries, but the disease can be devastating.

Type B meningococcal disease has been linked to outbreaks on at least six college campuses across the country since 2013, including a death at UW-Madison in 2013.