This study was intended to measure seropositivities and the level of mumps- and rubella-specific IgG of MMR vaccinees from 12 to 17 years of age in Korea.

From May 1996 to July 1996 we obtained sera from students of 1 middle and 2 high schools in Seoul, who were MMR vaccinees from 12 to 17 years of age and had no evidence of immunodeficiency. These 216 study population include 110 males and 106 females. Mumps- and rubella-specific IgG antibody levels were measured by ELISA. Cut-off values for seropositivity were 20 U(Gamma Unit) in mumps and over 0.17 in rubella.

1) As age increased, seropositivities to mumps increased, being 68.4% in 12 year, 79.3% in 13 year, 72.2% in 14 year, 82.0% in 15 year, 87.5% in 16 year, 87.0% in 17 year, which however has no statistical significance. 2) As age increased, the level of mumps-specific IgG antibody(mean±standard deviation, GU) increased, being 52.0±49.2 in 12 year, 65.9±51.4 in 13 year, 71.1±66.0 in 14 year, 67.8±53.6 in 15 year, 82.8±67.8 in 16 year, 92.0±68.9 in 17 year, which however has no statistical significance. 3) As age increased, seropositivities of rubella-specific IgG increased significantly, being 26.3% in 12 year, 20.7% in 13 year, 50.0% in 14 year, 67.2% in 15 year, 66.7% in 16 year, 65.2% in 17 year(P<0.001). 4) As age increased, rubella-specific IgG increased significantly, being 0.13±0.145 in 12 year, 0.087±0.101 in 13 year, 0.194±0.168 in 14 year, 0.260±0.187 in 15 year, 0.305±0.213 in 16 year, 0.325±0.221 in 17 year(P<0.001). There was positive correlation between age and rubella-specific IgG titer(rubella-specific IgG=0.0517×age−0.5586, r=0.3752, P<0.001).

In adolescent, seropositivities and the level of mumps-specific IgG remained relatively high, but approximately 20% of study population showed seronegativity. Seropositivities and the level of rubella-specific IgG showed the lowest level at 13 years of age and were increased with age after 14 years of age. Further evaluation may be needed to elucidate the cause of these changes of rubella-specific IgG.