Adverse reactions such as fever may still occur with the second MMR vaccination, but are significantly less likely to occur than with the first dose. Adverse effects of the first dose of MMR vaccine are generally more pronounced than those of the second and third doses, including fever symptoms. Since the first dose has already caused the body to produce certain antibodies, which have a protective effect, the second dose of MMR vaccine virus will be partially neutralized by the antibodies when it enters the body, so the adverse reactions of the second dose are lower than those of the first dose, but they may still occur. Fever after MMR vaccination is a common adverse reaction of vaccine, which commonly occurs 7-12 days after vaccination, usually mild fever, which can be relieved by resting for 1-2 days without special treatment. If moderate fever, that is, the body temperature reaches 38-39 ℃, or more than two days has not been relieved, should be given in time to the physical cooling, such as parents can lower the room temperature, give more water to the child, or follow the doctor’s advice to use antipyretic drugs. If the body temperature exceeds 39 ℃, should promptly seek medical attention to avoid the emergence of febrile convulsions. The child’s condition is changing rapidly, if there is recurrent fever or mental instability need to seek timely medical treatment.