Durability of the Mumps Antibody Response After the Third Dose of MMR Vaccine

BACKGROUND: A third dose of measles, mumps, and rubella vaccine (MMR3) may be administered in outbreak and nonoutbreak settings. However, data on long-term immunogenicity to the mumps component of MMR are limited. We examined durability of mumps antibody response among adults up to 11 years after receipt of MMR3. METHODS: Persons who received MMR3 at ages 18-28 years had sera collected before (baseline), 1 month, 1, 5, and 9-11 years after vaccination. Mumps antibodies were assessed by plaque reduction neutralization, immunoassay (EIA), and immunoglobulin G (IgG) avidity. Neutralizing antibodies were assessed against the vaccine strain (Genotype A) and a wild-type virus from Genotype G. Participants with neutralizing antibody titers <31 for Genotype A and <8 for Genotype G, and with EIA index values <1.10 were considered potentially susceptible. RESULTS: Among participants with data for all visits after MMR3 (40%, n = 262/655), susceptibility based on Genotype A titers increased from 15.7% (41/262) at baseline to 30.5% (80/262) 9-11 years after vaccination while susceptibility based on Genotype G titers remained relatively stable (30.2%-24.2%). The proportion of participants seronegative for mumps IgG by EIA increased from 0% (0/255) at baseline to 7.5% (19/255) 9-11 years after vaccination. The avidity index increased from 52% to 67% through Year 5 (P < .0001). CONCLUSIONS: By 9-11 years after receipt of MMR3, many participants had mumps antibody levels that predicted susceptibility to infection, comparable to those observed before receipt of MMR3. The antibody titers to Genotype G remained consistently lower than the titers to the vaccine strain.