Spitting up after MMR vaccination may be caused by adverse reaction to the vaccine, cold or indigestion, which may be abnormal. If your baby spits up after the MMR vaccine, it may be an adverse reaction caused by the MMR vaccine, and your baby may experience symptoms such as vomiting, loss of appetite, or localized redness, swelling, fever, rash, etc. If the symptoms are more pronounced, you need to take your baby to the hospital for medical attention. In addition, babies spitting up after the MMR vaccine may also be caused by other reasons, such as indigestion caused by the baby getting cold or overfeeding the baby, not necessarily due to the side effects of the vaccine. Spitting up after the MMR vaccine may also have other causes, it is recommended to go to the hospital in a timely manner, complete the examination to determine the cause of the disease, under the guidance of the doctor to give targeted treatment or therapy.