Affinity and sub-class distribution of IgG-class antibodies following vaccination with a live rubella virus vaccine.

Thirty-three seronegative adolescents were vaccinated with a live rubella vaccine. Serum samples were collected 2 weeks, and 1, 2, 6 and 12 months later. Antibodies were analysed by using ELISA and monoclonal antibodies to different subclasses of human IgG. A proportion (10 out of 33, 30%) of the vaccinees developed low amounts of rubella IgG-class (both IgG1 and IgG3 isotypes) antibodies. There was no difference between the high and low responders when the IgG-class antibodies were measured at low serum dilutions suggesting that the affinity of the antibodies was probably equal. Our results point out a possible pitfall, development of low amounts of antibodies, in the serological evaluation of the success of rubella vaccination.