MMR vaccine usually refers to the MMR vaccine. You will probably have a fever for about 1~2 days after the vaccination, but there are some people who do not have a fever in their body after the vaccination, and the exact time of occurrence is also related to the individual’s physical condition. MMR vaccination can prevent three common acute respiratory infections in children: measles, bleeding mumps and rubella. In 7~12 days after vaccination, some children may have mild fever, skin rash or swollen lymph nodes in the neck, which is a common adverse reaction, and the symptoms will gradually subside on their own. The occurrence of fever after vaccination is considered to be the fact that MMR vaccine itself is a virus, and the human body will have a slight immune response after vaccination, thus triggering fever. If the child’s physical condition is relatively poor, the fever will last for about 1~2 days after vaccination. If the individual is in good physical condition, fever does not usually occur. It is recommended that if the fever persists or worsens, the child should go to the hospital in a timely manner to avoid adverse consequences.