Decreased humoral immunity to mumps in young adults immunized with MMR vaccine in childhood

Abstract

Significance The live-attenuated mumps-measles-rubella (MMR) vaccine has been highly successful in the United States since its introduction 47 years ago. However, for the past decade, mumps outbreaks have been occurring among young adults who were vaccinated as children. Waning immunity has been proposed as a key contributing factor to mumps resurgence. In our sample ( n = 71) of 18- to 23-year-old college students, the majority had detectable mumps IgG antibodies by enzyme-linked immunosorbent assay (ELISA) but the magnitude was lower than rubella. Neutralizing antibody titers were 6-fold lower to a circulating genotype G mumps strain versus the vaccine strain. Ten percent of our participants had no detectable memory B cells to mumps. Strategies are needed to improve immunity to the mumps vaccine.