Measles-mumps-rubella (MMR) vaccination has decreased the incidence of measles, mumps, and rubella virus infections in several countries. However, the persistence of MMR vaccine-induced immunity in the absence of endemic infection has remained unknown.
The persistence of cellular and humoral immunity to mumps virus was studied in 50 individuals (group A) who had been vaccinated twice with MMR vaccine during early childhood and were followed up for 21 years after their first vaccination. Eleven individuals (group B) with naturally acquired immunity to mumps virus were studied for comparison.
Anti-mumps virus IgG antibodies were detectable (titer > or = 230) in 72% of the vaccinees. A mumps antigen-specific lymphoproliferative response (defined as a stimulatory index [SI] > or = 3) was observed in 98% of group A subjects (mean+/-SD SI, 26+/-30 [range, 0.5-252]) and in 100% of group B subjects (mean+/-SD SI, 22+/-27 [range, 5-123]). Significant mumps antigen-specific interferon- gamma production was detected in 73% of subjects in both groups A and B, and interleukin-10 production was detected in 40% and 36% of group A and B subjects, respectively.
All presently seronegative vaccinees (n=14) had mumps antigen-specific lymphoproliferative responses, and only 1 of the seropositive vaccinees (n=36) was devoid of detectable cellular immunity. The results suggest a very long persistence of vaccine-induced anti-mumps virus cellular immunity.