Some infants may develop a fever after vaccination, with their body temperature slightly higher than normal. The ingredients in the vaccination are substances similar in structure to certain types of viruses, which will cause the body to react and produce antibodies, so it is normal for infants to have a fever after the vaccination. As long as the temperature is below 38.5 degrees Celsius, there is no need to worry too much, nor should you take fever-reducing medication indiscriminately, just let them drink more water and rest more. If your baby has a high fever and is crying because he or she is uncomfortable, you can actively cool him or her down by using fever patches and cold towels to reduce fever in the forehead and underarms. However, do not let the chest and belly get cold, otherwise it will be easy to catch a cold. Babies with extremely high fever after vaccination, exceeding 38.5 degrees Celsius and lasting for a long time, with burning red cheeks, need to be seen promptly. It may be that the baby has a more serious rejection reaction to the vaccination, and to avoid serious consequences, you should go to the hospital for consultation. Many babies have a fever after vaccination, and usually recover on their own in a day or two, but if the reaction is more severe and serious, you should see a doctor.