COMPARATIVE-STUDY OF REACTOGENICITY AND IMMUNOGENICITY OF NEW AND ESTABLISHED MEASLES, MUMPS AND RUBELLA VACCINES IN HEALTHY-CHILDREN

Concerns about the association of aseptic meningitis with measles-mump s-rubella (MMR) vaccines containing the Urabe Am 9 strain and the incr easing worldwide demand for MMR vaccines, prompted the development of a new mumps vaccine strain (RIT 4385) by SmithKline Beecham Biological s (SIB) as part of a trivalent live attenuated MMR vaccine. The presen t study assessed the immunogenicity and reactogenicity of two lots of 'Priorix' with a widely used and established vaccine M-M-R II (Merck & Co. Inc.) as comparator vaccine. 255 healthy children, 12 to 24 mont hs of age, were enrolled in a single-blind study and randomly allocate d to receive a single dose of one of two lots of ''Priorix'' or M-M-R II vaccine. Vaccinees were followed up for six weeks post-vaccination for solicited and unsolicited symptoms. Immunogenicity was determined in pre- and 60 days post-vaccination sera using commercial immunoassay s for measles, mumps and rubella antibodies. There were no significant differences in immune responses between groups for any of the three v accine components. In initially seronegative subjects, the respective post-vaccination seroconversion rates for 'Priorix' lots 1 and 2, and M-M-R II were 100, 100 and 97.6% for measles antibodies, 91.7, 95.1 an d 94% for mumps antibodies and 100, 100 and 100% for rubella antibodie s, respectively, GMTs for the three groups were 3,076, 3,641 and 5,173 mIU/ml for measles antibodies, 934,900 and 1,043 U/ml for mumps antib odies, and 86.4, 87.5 and 97.1 IU/ml for rubella antibodies, respectiv ely. The incidence of local symptoms was significantly lower for both 'Priorix' lots (17.6 and 15.3% for lots 1 and 2, respectively) than fo r M-M-R II (37.6%), Fever greater than or equal to 38.1 degrees C duri ng the six-meek observation period occurred in approximately 25% of al l subjects in all groups with no differences between the groups. No pa rotid/salivary gland swelling or signs of suspected meningism were rep orted, and there were no serious adverse events related to vaccination . The new MMR vaccine 'Priorix' containing the new RIT 4385 mumps stra in was safe and had a significantly improved local tolerability profil e over the comparator vaccine, M-M-R II, while eliciting an at least e quivalent immune response.