
Despite routine use of a childhood vaccine, the United States still sees outbreaks of mumps. Now, a new study reinforces the belief that it’s due to waning immunity post-vaccination. Mumps is a viral infection best known for causing puffy cheeks, a swollen jaw, fever and general misery. While it’s usually relatively mild, mumps occasionally causes serious complications like brain inflammation and hearing loss. Because of that, children in the United States are routinely immunized against mumps, using the measles-mumps-rubella (MMR) vaccine. Yet mumps has seen a resurgence in the past two decades. Since 2006, there has been an uptick in annual cases — often among college-age adults who were vaccinated as children, according to the U.S. Centers for Disease Control and Prevention. Similar patterns have been seen in other countries where vaccination rates are high, leading to two theories on why: waning immunity to mumps in the years after vaccination; or the emergence of new mumps strains that evade the vaccine-induced immune response. The new study — published Jan. 9 in the Proceedings of the National Academy of Sciences — supports the waning-immunity view. Using mathematical modeling, researchers found that waning immunity could largely explain the resurgence of mumps in the United States in recent years. They also estimated that about one-third of vaccinated kids start to lose their mumps immunity by age 18. But… read on > read on >