Acetaminophen Could Affect Shots’ Effectiveness

From The Oregonian  11/25/09

The Question: Acetaminophen is often given to infants who have just been vaccinated to keep them from developing a fever.  Might this affect the vaccine?

The Answer: Fever reducer may dampen effectiveness of shots.

The Study:  It involved 459 healthy infants who were getting normal childhood vaccinations or booster shots against pneumococcal disease, Haemophilius influenza type B (Hib), diphtheria, tetanus, polio, whooping cough, and rotavirus.  They were randomly assigned to be given acetaminophen every six to eight hours for 24 hours after their shot, or no acetaminophen.  Within four days, about 42 percent of the infants given acetaminophen after their first vaccination developed a fever of 100.4 degrees or higher, compared with 66 percent of similar babies not given acetaminophen.  After booster shots, the fever rate was 36 percent with the drug, 58 percent without it.  However, blood tests revealed what doctors call a “weakened immune response” in infants given acetaminophen, meaning they had fewer antibodies against the disease, lowering the protections that vaccination provides.

Caveats: The study tested only the effects of acetaminophen.   The effects of ibuprofen, which also can reduce fever, were not tested.  The study was funded by GlaxoSmithKline, which makes the vaccines used in the study.

Online:  Learn more about childhood vaccinations at www.fda.gov (search for “parent’s guide”) and www.familydoctor.org.