No Risk of Recurrent Seizures From Childhood Vaccines

From the WebMD Archives

Aug. 29, 2001 -- Getting kids immunized is never fun, but a new study should help ease parents' fears about a side effect of some important vaccines.

Some kids have fever-related seizures after childhood vaccinations. But the study shows that it's unlikely that they will go on to have developmental problems or a recurrent seizure condition called epilepsy.

"That should be quite reassuring for parents," says study author Robert L. Davis, MD, MPH, associate professor of pediatrics and epidemiology at the University of Washington in Seattle. The study appears in this week's New England Journal of Medicine.

Davis tells WebMD that so-called febrile seizures "can be quite concerning." When one happens, a child's entire body shakes, his or her muscles jerk, and the child loses consciousness. As a rule, these seizures usually last longer than 30 seconds, and when the child is conscious again, he or she is usually sleepy and disoriented.

The seizures can occur while a child is battling a cold, an ear infection, or a range of other infections that happen during childhood.

Doctors have long recognized that some kids have febrile seizures after two types of childhood vaccinations: DTP (diphtheria, tetanus, and pertussis) and MMR (measles, mumps, and rubella) vaccines. However, experts have not known whether these early seizures trigger problems later on.

Davis' study, the largest of its kind to date, looked at more than 300,000 kids in four large HMO plans, tracking the occurrence of seizures related to DTP and MMR.

After examining the medical records of children who experienced fever-related seizures between 1991 and 1993, researchers found that "the risk of febrile seizures is quite rare," Davis tells WebMD. Children were at risk for a febrile seizure only on the day of the DTP vaccine or eight to 14 days after being immunized for MMR.

They also found that "even if there was a febrile seizure, there was no long-term damage from it. the febrile seizures caused by these vaccines aren't anything out of the normal," says Davis. "These children are not at any increased risk of epilepsy or autism or other developmental disabilities."

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Since the study, the DTP vaccine has been changed in the U.S., he says. In 1996, the FDA approved a new DTP vaccine containing a different type of pertussis. The new vaccine is called DTaP and "is associated with lower rates of fever and is likely to show an even weaker risk for seizures, which should be even more reassuring for parents," he says.

While it's possible to prevent febrile seizures by giving kids Tylenol, he advises parents to talk to their doctor beforehand. "No medication is risk-free," he adds. "We don't want to promote the indiscriminate use of Tylenol."

Davis' study is indeed good news, says Thomas Saari, MD, professor of pediatrics at the University of Wisconsin Medical School in Madison. "It's always been hard to know whether a child is having a febrile [seizure] due to the vaccine or to some illness," he tells WebMD.

Why some kids get more febrile seizures than others has always been somewhat of a mystery, he says. "We wish we could identify those kids beforehand, but we just can't. Parents just have to do their best to keep febrile seizures from occurring."

With the availability of the DTaP vaccine, Saari says he's quit telling parents to give kids Tylenol after that shot. Since MMR fevers occur about a week or two after the shot, "it's much more difficult to anticipate when fever is likely to happen. So we counsel parents that if kids do develop a fever, give them Tylenol." Parents should never give aspirin to children under age 18, because of the risk of Reye's syndrome, a rare but dangerous disease.

Saari says his main concern is when children don't get immunized. "They have a greater chance of developing significant central nervous system problems as a result of disease ... permanent brain damage and persistent seizure problems," he says. "It can be very sobering. It's why immunizations are so important."

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