Safety and characterization of the immune response engendered by two combined measles, mumps and rubella vaccines.

We performed a randomized trial to compare the safety and immunogenicity of two combined measles, mumps and rubella vaccines in healthy children 14-24 months of age. Triviraten Berna Vaccine (Swiss Serum and Vaccine Institute), contains the Edmonston Zagreb 19 strain of measles virus, the Rubini mumps virus strain and the Wistar RA 27/3 rubella strain while MMR-Vax (Merck, Sharp & Dohme, West Point, PA) contains the Enders attenuated Edmonston measles strain, the Jeryl Lynn mumps strain and the Wistar RA 27/3 rubella strain. Immunization with Triviraten Berna was associated with a significantly lower incidence of swelling and redness at the injection site in addition to a reduced rate of fever compared with MMR-Vax. Seroconversion rates for the measles and rubella vaccine components were comparable in all tests used. However, seroconversion for the mumps vaccine component was test-dependent. Using an ELISA, the seroconversion rate following immunization with MMR-Vax was significantly (P < 0.01) higher than for Triviraten Berna. In contrast, nearly identical rates were obtained using an indirect immunofluorescence test. Both vaccines were equally effective at engendering antibodies capable of neutralizing wild type mumps virus. Geometric mean ELISA antibody titers against measles and mumps virus were higher following immunization with MMR-Vax while that for rubella was higher after immunization with Triviraten Berna. A small number (N = 13) of adolescents immunized either with MMR-Vax or Triviraten Berna were reimmunized with Triviraten Berna and various humoral and cellular response parameters to the measles and mumps vaccine components analyzed. While few subjects mounted a humoral antibody response to measles, most likely due to elevated baseline titers, there was a marked lymphoproliferative response. Anti-mumps virus ELISA antibody titers were higher both at baseline and after reimmunization in subjects who received MMR-Vax for primary immunization. However, there was no difference in either neutralizing titer or proliferative response in subjects primed with MMR-Vax or Triviraten Berna either before or after reimmunization.