Hold the Tylenol after getting a vaccine.

Children typically get fevers after certain vaccination shots. The rise in body temperature is a sign that the child is developing an immune response to the vaccine. In other words, a fever post-shot (if it occurs) is a sign that the vaccine is kicking in.

Dr. Robert T. Chen at the U.S. Centers for Disease Control explains that a child’s immune system is processing the immunization and providing them with the best protection. Since this post-shot fever happens to many children, they are often given acetaminophen (Tylenol is a popular brand) to avoid the fever response all together. Trying to stop this fever-response may actually be counter-productive.

A study shows, this fever preventive protocol given by some doctors can decrease the effectiveness of the vaccine they had just administered.

In the October 17 issue of The Lancet, Dr. Chen adviced that “unless your doctor specifically recommends it, do not give fever-reducing medicines at the same time as vaccination to prevent your child from developing a fever. “

It is still okay to use fever-reducing medications (like acetaminophen or ibuprofen) to treat an existing fever. Just do not give it to prevent the fever.

The studies that shed light on all this was done by a team of researchers led by Dr. Roman Prymula from the University of Defence in Hradec Kralove, the Czech Republic. The team conducted two studies – one when children got their first vaccination, another when they got their booster shot.

The vaccines involved in the studies: pneumococcal disease, Haemophilus influenza type b (Hib), diphteria, tetanus, whooping cough, hepatitis B, polio and rotavirus.

459 babies were observed. Some were assigned to get acetaminophen every six to eight hours for 24 hours after vaccination. Some were given no acetaminophen at all.

Those who received the anti-fever meds had less incidence of fever, but they also had a decreased immune response to the vaccines given. Lab tests showed that these babies developed less antibodies – specifically to Hib, pneumococcal disease, diphteria and tetanus toxoids and an antibody for whooping cough.

The theory is, acetaminophen’s anti-inflammatory properties interfere with the healthy immune system’s antibody responses. The result is weakened immunization.

Infectious disease specialist Dr. Marc Siegel at the New York University of Medicine explains that “the conclusion that Tylenol not only suppresses fever, but also decreases immune response is plausible. After all, what is an immune response? It’s an inflammatory response.”

Something to bear in mind, next time we take a trip to the pediatrician’s office for the next round of vaccinations. Talk to your doctor about this as each child is different. Some children with a history of febrile convulsions (convulsions brought on by fevers), may need a fever-preventive protocol. Most kids may be better off not stopping the vaccine-response fever. Your trusted pediatrician should know what’s best for your child.

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