Recent mumps outbreaks are raising questions about strategies to combat the spread of the virus. One issue of concern is that the current vaccine is designed to protect against a different strain of the virus than the one that is sparking the outbreaks. Though the vaccine can help prevent some people from getting the disease or minimize its effects, the outbreaks have raised questions about whether a new vaccine is needed. We spoke to Stanley Plotkin, an expert on vaccines and a member of the editorial board of the journal Clinical and Vaccine Immunology, about what’s driving the outbreak, whether boosters can adequately address the problem, and why developing a new vaccine is not an easy solution to the problem.