Does Tylenol Blunt Vaccine’s Effectiveness?

The results of a study reported in this month’s issue of The Lancet may be big news for pediatricians and moms everywhere.

Many of us routinely give acetaminophen (Tylenol is the trade name) to infants and kids just before or after immunizations. The idea is to prevent or reduce the mild fever and soreness associated with the vaccine.

But that’s not a good idea, finds an international research team led by Roman Prymula, MD, of the University of Defense, Czech Republic.  Prymula and colleagues set out to look at whether common over-the-counter remedies work to prevent vaccine-related fever.  What they found was that they may dampen the vaccine-induced immune response.

Robert T. Chen, MD, chief of vaccine safety for the CDC’s National Immunization Program explains the results this way:  “A fever is likely a critical part of the immune response to any infection or vaccination, so dampening fever after immunization is probably not a good idea for most kids,” Chen tells WebMD.

The truth is, we tend to rush to medicate any fever in a small child, and maybe the message here is that we should re-think that habit. Fever serves a biological purpose.  It’s part of the body’s way of fighting invaders.  The results of this study indicate that an increase in body temperature helps ramp up the immune system’s antibody machinery, and that’s important new information.

It’s unclear whether other over-the-counter drugs such as ibuprofen (Motrin and Advil) have the same effect, but experts say until more is known all fever-reducers should be avoided when vaccines are given.  Aspirin should never be given to children with fever because of the risk of Reye’s syndrome.

So next time your little one feels warm, take a minute to think about whether a fever reducer is really necessary, and skip it entirely at vaccine time.