It is common for babies to develop a fever after a flu shot. The fever is rarely serious and the temperature of the fever is relatively low, in most cases below 38 degrees. In addition, the duration of the fever is not particularly long, and the body temperature can return to normal after 2-3 days, and the child will not be significantly uncomfortable. However, there are special circumstances that can cause fever to be more severe. In order to raise the body temperature, the body’s heat dissipation will be reduced and heat production will be increased, resulting in fever. In this case, treatment under medical supervision is required. For high fevers, antipyretic drugs such as acetaminophen pellets or acetaminophen suspension are also needed.