Effect of simultaneous administration of live measles vaccine on the "take rate" of live mumps vaccine.

During the course of clinical studies to develop a new bivalent measles-mumps vaccine, it was established that simultaneous administration of live measles and mumps vaccines at doses contained in the monovalent vaccines resulted in a reduced seroconversion rate against mumps but not against measles. This one-way interference was resolved by increasing the dose of the mumps component in the bivalent measles-mumps and the trivalent measles-mumps-rubella vaccines above that in the monovalent mumps vaccine. On the other hand, it was not necessary to adjust the doses of the measles and rubella components in the combined vaccines. This observation requires that not only the titres of vaccine viruses must be carefully adjusted in combined live mumps vaccines but also that the heat-stability of each component in such vaccines be carefully determined to ensure that interference is not a problem during the complete shelf-life of the product. The relative doses at release of combined mumps vaccines using the Urabe Am 9 strain and the heat-stability characteristics of these products will be presented and discussed.