From Vaccines: Fever can be low grade for 24-48 hours after vaccine administration and does not require a fever reducer. The fever is the body’s way of building an immune response to the vaccine.
From Illness: Fever from an illness is a sign that your child’s body is building an immune response to the infection. The fever will help your child’s body fight the infection. Any fever rectally >100.4F in a 0-60 day old child is critical and warrants immediate evaluation at our office during the day or the ER at night. If the child is 3 months or older with fever and is still feeding well, then there is a lower risk of a problem. Signs of potential trouble are: fever >102 and your child is visibly uncomfortable, excessive sleepiness, poor feeding, abnormal rash, seizure, fast breathing, fever for more than 5 days. Any child with a fever >104F should be seen by their primary provider. Fever in a child with a serious medical condition such as cancer, heart problems, kidney problems, spleen removed, etc. should be seen by a provider.
Treatment of Fever: See our charts for Tylenol or Ibuprofen dosages on our website under Medical Advice. We recommend a fever reducing medication when the fever is >102F. Fever is your friend to kill the pathogen infecting your child. AVOID all aspirin products for children because of a rare condition called Reye syndrome. You can also have your child take a tepid, not cold but lukewarm bath which can help one feel better. You can also use cool compresses to the forehead and pulse points on wrists and ankles to help.

For more information about fevers follow this link!