Three different doses of the F-genotype attenuated mumps vaccine , A ( 3.5 0.25 logCCID50 ) , B ( 4.25 0.25 logCCID50 ) and C ( 5.0 0.25 logCCID50 ) , as well as a placebo control and a positive control of a licensed A-genotype vaccine ( S79 strain ) were used .