The baby appeared fever the next day after the vaccine, do not exclude the adverse reaction of the vaccine, this situation is also relatively normal, a part of the child after the vaccine, there will be a mild fever, pay attention to monitor the body temperature, drink more water, 2-3 days the body temperature can be lowered. Because most of the vaccines are inactivated bacteria or viruses, there may also be toxins, these substances will stimulate the thermoregulatory center, resulting in certain abnormalities in the thermoregulation point, so there will be an increase in body temperature, resulting in fever, usually not particularly serious, the fever is not particularly high, and the duration of the fever will not be particularly long, usually 2-3 days can be returned to normal. However, some children’s body temperature will be higher, this time the first thing to do is to reduce fever, otherwise it is easy to occur the phenomenon of febrile convulsions, the child’s brain cells or brain function damage, it is recommended that the physical lowering of temperature or oral ibuprofen suspension.