If the baby cries after the MMR vaccination, it may be due to adverse reactions such as pain at the site of the needle hole, fever and rash. If the crying occurs right after the injection, it may be that the vaccine injection site is at the attachment of the lower edge of the deltoid muscle on the outer side of the upper arm, so the injection will leave a needle hole. At the same time, the vaccine is also irritating, so there will be pain from the needle holes as well as pain from clothing rubbing, causing the baby to cry. In addition, if crying occurs some time after the injection, there may be a transient mild fever that causes the baby to be uncomfortable and cry. If the baby is observed to have a rash, it may be a side effect of the medication that has caused the rash, resulting in crying. After the MMR vaccine, the baby crying, there may be other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.