This study is a randomized, blind, single-center, controlled phase III clinical trial. The purpose of this study is to evaluate the immunogenicity and safety of a live attenuated mumps vaccine manufactured by Sinovac (Dalian) Vaccine Technology Co., Ltd. The control vaccine is a commercialized live attenuated mumps vaccine manufactured by Zhejiang VACN bio-pharmaceutical Co. Ltd. All participants are healthy infants between 8 - 18 months old, and will be randomly assigned into experimental group or control group in the ratio 1:1.