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August 29, 2001

Study confirms link between vaccines and seizures, but shows that seizures pose no lasting risk

Seattle—Parents concerned about the link between childhood vaccinations and seizures need not worry, according to new research conducted by Group Health Center for Health Studies and the University of Washington.

Children who suffer rare fever-related seizures after getting DTP (diphtheria, tetanus, and pertussis) and MMR (measles, mumps, and rubella) vaccinations do not have an increased risk for subsequent seizures or neurodevelopmental disabilities.

The new research, published in the August 30 issue of the New England Journal of Medicine, confirmed that DTP and MMR vaccinations may temporarily increase the risk for fever-related seizures, also called "febrile seizures," in some children. But the study also confirmed the findings of smaller studies that these vaccinations are not linked with more serious kinds of seizures, such as those associated with epilepsy.

The study was conducted among nearly 680,000 children enrolled in four health plans. "This is the largest study to suggest that these vaccines pose no increased risk for serious long-term consequences," says Robert L. Davis, MD, MPH, of Group Health Center for Health Studies and the Departments of Pediatrics and Epidemiology at the University of Washington. Davis is a co-author of the journal article, along with lead author William E. Barlow, PhD, a biostatistician and senior investigator at Group Health Center for Health Studies.

The four health plans involved—Group Health Cooperative and three Kaiser Permanente HMOs—are part of the Vaccine Safety Datalink project, coordinated by the U.S. Centers for Disease Control and Prevention. The project includes one of every 40 children in the United States under age 7 years.

Researchers examined the medical records of children who experienced fever-related seizures between 1991 and 1993. "We found that a child's fever-related seizure did not result in any lasting adverse consequences for the child," said Barlow. "In addition, we found that children vaccinated with DTP are most at risk for seizures on the day of the vaccination. Previously it was believed that the risk period was the same for three days following the shot.

In a parallel study, the researchers also discovered that they could learn about the safety of vaccines using computerized data rather than conducting more labor-intensive reviews of individual medical records. Use of automated systems will allow for the rapid assessment of health, the authors wrote. Such need was apparent last year when manufacturers of a new rotavirus vaccine pulled the vaccine off the market following concerns about its link to bowel problems in children.

MMR vaccine is typically given in two doses, one at age 12 to 15 months, and one at age 4 to 6 years. Until 1993, DTP vaccine was given to children ages 2 months to 6 years in a series of five doses. Since then, DTP vaccine has been largely replaced in the United States with a new form of vaccine called DTaP, which has fewer side effects. Group Health is currently conducting research to study the safety of this vaccine as well.

Group Health Center for Health Studies conducts epidemiologic, health-services, and clinical research related to prevention, diagnosis, and treatment of major health problems. The Center also evaluates the efficacy and cost-effectiveness of health care services and technologies. Funded primarily through government and private research grants, the Center is located in Seattle, Washington.

Group Health Cooperative is the nation's largest consumer-governed health care system, serving nearly 600,000 people in Washington and Idaho.

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Questions & Answers
Vaccine- and fever-related seizures: What should parents do?

Given the risk of seizures, should parents have their children vaccinated?

Yes. Despite the small risk for seizures linked to fever following vaccination, most pediatricians strongly recommend vaccination. Vaccines prevent serious diseases that pose a much greater risk to most children's health than the seizures associated with vaccination. Pertussis, for example, is a highly contagious respiratory disease ("whooping cough") that can lead to pneumonia, brain damage, and even death. Tetanus, diphtheria, measles, and mumps can also be life-threatening. Rubella can cause pregnant women to miscarry or have babies with serious birth defects.

What can be done to prevent fever-related seizures following vaccination?

Many pediatricians recommend giving children an aspirin-free pain reliever such as acetaminophen (Tylenol®) at the time the child receives DTP or DTaP. DTaP is new vaccine with fewer side effects that has recently replaced most DTP in the United States. Do not give aspirin to a child under 18. Aspirin can cause Reye's Syndrome, a rare but dangerous disease.

Seizures following DTP usually occur in the first three days following immunization, with the greatest frequency happening in the first 24 hours.

Preventing seizures following an MMR vaccination is more difficult because fever-related seizures typically occur eight to 14 days following the shot. Still, it may be helpful to start giving your child an aspirin-free pain reliever as soon as you notice a fever.

What should you do if your child has a seizure following a vaccination?

Contact a medical professional right away. Although fever-related seizures typically are not associated with long-term harmful effects, it's important that your child be evaluated to rule out other possible health problems.

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