[Specific humoral immunity after single immunization with mumps vaccine: data of a 3-year follow-up].

The level and spectrum of humoral specific immunity were studied in 60 volunteers immunized with Russian mumps vaccine. Specific IgG levels were measured by enzyme immunoassay (EIA) and neutralization test using the Leningrad-3 (L-3) mumps virus (MV) vaccine strain and 5 heterologous MV strains of various genotypes (A, B, C, D, and H). The maximum functional activity of antibodies was recorded at an average of 18 months postvaccination. Within 3 years after vaccination, starting at 6 months, specific IgG neutralized all 6 MV strains having varying activity in relation to the genotype. Neutralizing titers (NT) against the L-3 strain were 1.3-1.7-fold higher than those against heterologous MV strains throughout the follow-up. Despite a tendency towards lower specific IgG levels, within 3 years postvaccination, EIA IgG titers remained to be 2.5 -log, L-3 strain HT were -log, or more, and the titers against 5 heterologous MV strains were 2 -log2 or more in all the volunteers.