Immune responses to live attenuated and inactivated mumps virus vaccines in seronegative and seropositive young adult males.

Live attenuated mumps virus vaccine and Formalin-inactivated mumps vaccine were compared for their ability to induce antibody responses and cell-mediated immune responses as measured by a lymphocyte blast transformation test (LBT). The subjects studied were conscripts of the Finnish Defense Forces. In seronegative subjects antibody levels induced by attenuated virus were more variable than those induced by inactivated virus, including one failure with the live vaccine out of a total of nine subjects. IgM antibody class response was seen only in four of nine subjects vaccinated with live virus--in those subjects with the highest post-vaccination antibody levels and strongest LBT responses. Increases of antibody levels in originally seropositive subjects were higher in subjects vaccinated with inactivated virus. Cell-mediated immunity induced by both vaccines was relatively poor when measured by the LBT test. At a time of 6-8 months after vaccination, LBT responses in originally seronegative subjects were not observed.