Concerns about the association of
aseptic meningitis with
measles-
mumps-
rubella (MMR)
vaccines containing the Urabe Am 9 strain and the increasing worldwide demand for MMR
vaccines, prompted the development of a new
mumps vaccine strain (RIT 4385) by SmithKline Beecham
Biologicals (SB) as part of a trivalent live attenuated
MMR vaccine. The present 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 months of age, were enrolled in a single-blind study and randomly allocated 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 immunoassays for
measles,
mumps and
rubella antibodies. There were no significant differences in immune responses between groups for any of the three
vaccine 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 and 94% for
mumps antibodies and 100, 100 and 100% for
rubella antibodies, respectively. GMTs for the three groups were 3,076, 3,641 and 3,173 mIU/ml for
measles antibodies, 934, 900 and 1,043 U/ml for
mumps antibodies, and 86.4, 87.5 and 97.1 IU/ml for
rubella antibodies, respectively. The incidence of local symptoms was significantly lower for both '
Priorix' lots (17.6 and 15.3% for lots 1 and 2, respectively) than for M-M-R II (37.6%).
Fever > or = 38.1 degrees C during the six-week observation period occurred in approximately 25% of all subjects in all groups with no differences between the groups. No parotid/salivary gland swelling or signs of suspected
meningism were reported, and there were no serious adverse events related to vaccination. The new
MMR vaccine '
Priorix' containing the new RIT 4385
mumps strain was safe and had a significantly improved local tolerability profile over the comparator
vaccine, M-M-R II, while eliciting an at least equivalent immune response.