Mumps is a highly contagious viral infection characterized by swelling of the salivary glands and accompanied by fever, fatigue, body aches, and appetite loss. Severe complications of the disease include pancreatitis and encephalitis. A recent report from the Centers for Disease Control and Prevention (CDC) describes a recent, ongoing outbreak of mumps in the United States.

Commonly referred to as a “childhood disease,” mumps affects people of all ages, but it is largely preventable by vaccination. The vaccine is delivered in two doses, typically over a period of a few years, in combination with vaccines against measles and rubella. A single dose of the vaccine reduces the risk of mumps infection by 78 percent; two doses reduce risk by 88 percent.

The outbreak began in August 2019 when 30 people who attended a wedding in Nebraska later developed the disease. The index patient was not only asymptomatic but was also fully vaccinated. Eventually, 62 patients (41 of whom were fully vaccinated) were diagnosed with mumps related to the index case.

Vaccines are the cornerstone of public health programs to prevent disease and death. Unfortunately, vaccination rates for children have dropped due to the ongoing COVID-19 pandemic. A mumps outbreak in a highly vaccinated population emphasizes the importance of vaccination to prevent spread to unvaccinated people but also raises questions about presumed lifelong immunity from childhood vaccines.

• Link to CDC’s Morbidity and Mortality Weekly Report