Vaccines and Tylenol

Many families worry when their babies receive vaccines. Some of the concerns are the pain and possible side effects from the shots.  I break down normal vaccine reactions into two main types.

The first is a local reaction:  mild redness and/or swelling at the injection site.  This very common, normal reaction will usually subside in the first day or so.  Applying a cool compress may be helpful to reduce the inflammation.  Severe swelling or redness that is spreading is not normal and should be seen by your doctor. 

The second normal vaccine reaction, which is usually more concerning to the family, is a more systemic reaction. This is when the baby’s immune system is “turned on” from the vaccination and the baby might feel cranky and/or develop a fever for the first 24-48 hours after the shots.  This is a normal, expected side effect that does not happen every time, but is not worrisome or unexpected.  If the fever persists, is very high, or the baby seems extremely irritable or lethargic, your doctor should be notified. 

Frequently, parents try to prevent the fever and crankiness by pre-medicating their babies with Tylenol (acetaminophen).  In the past, this practice was not discouraged.  In fact, the CDC’s advisory panel says it is reasonable to pre-medicate children at high risk for developing seizures, which can be triggered by fevers.  However, a recently published study showed slightly lower protective antibody levels from vaccines in infants who were pre-medicated with Tylenol versus infants who did not receive Tylenol – meaning, the vaccine might not have been as affective. The effect of the decreased levels might be small, as the vast majority of the pre-medicated infants did achieve protective antibody levels after their booster doses. Even so, the evidence in the study does point to stopping the practice of pre-medicating to try to prevent this reaction. 

Of importance, there is no evidence that the same decrease of antibody levels occurs when a fever reaction is treated by Tylenol. In summary, not pre-medicating with Tylenol, but giving it if fever develops might give the best benefit of immunization.

All information given is not a substitute for the advice of your pediatrician, primary care provider or trained health professional.  Always consult with your pediatrician or health care professional.