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What's New - Vaccine Risks

Researchers confirm increased risk of fever-related seizure from two vaccines, but show seizures pose no lasting health risk

Study looked at records from 680,000 children, including 50,000 in Oregon and Southwest Washington

(PORTLAND, Ore.) – A new study being published in the August 30 issue of New England Journal of Medicine confirms that two types of vaccines were linked to higher rates of fever-related (febrile) seizures, although the actual numbers of children affected were low. However, the same study found that children who had the seizures after vaccination showed no lasting effects from them. Researchers followed for several years the children who’d had seizures. They reported no higher incidence of learning or developmental disability in children who’d been vaccinated and had seizures compared to children who’d had febrile seizures unrelated to vaccination. They also said the study confirms findings of earlier research that these vaccinations aren’t linked to more serious kinds of seizures, such as those associated with epilepsy.

Researchers with the Vaccine Safety Datalink project (made up of Kaiser Permanente and Group Health Cooperative and coordinated by the U.S. Centers for Disease Control) reviewed the medical records of 51,719 children enrolled in Kaiser Permanente in Oregon and Southwest Washington, as well as the records of another 572,782 California children covered by Kaiser Permanente and 55,441 Washington State children insured by Group Health Cooperative. The records were from 1991 to 1993.

The study shows that at most about one child in every 11,111 (or as few as one in every 16,666) suffered a seizure after a DPT vaccination (a combined shot protecting against diphtheria, whooping cough and tetanus). The rate was at most one child experiencing a seizure for every 2,941 children (or as few as one in every 4,000) vaccinated against measles, mumps and rubella (the MMR vaccine).

The study’s lead author is William E. Barlow, PhD, a biostatistician and senior investigator at Group Health Cooperative’s Center for Health Studies (CHS) in Seattle. Co-authors include John Mullooly, PhD, from Kaiser Permanente’s Center for Health Research in Portland and recently retired Kaiser Permanente Northwest pediatrician John Pearson, MD.

Dr. Pearson, who served as a neurology consultant to the study, says one side effect some children have when vaccinated is a rise in body temperature. It is that elevated body temperature which is believed to sometimes bring on a seizure, not the vaccination itself.

“Fever-related seizures occur with some regularity in children under age 5, most commonly due to fever from an infection,” says Dr. Pearson. “During a seizure, a child may stiffen and shake. Naturally, this is alarming to parents. This study should reassure parents that there are no harmful long-term effects to their children from fever-related seizures, whether from vaccination or routine childhood infections,” he says. “Parents have far more to fear from their children coming down with vaccine-preventable diseases, such as whooping cough or measles. These can cause lasting brain damage and even death.”

In countries where vaccinations have dropped off, such as Russia, Dr. Pearson warns that highly infectious childhood diseases quickly rebound, harming many unvaccinated children and teenagers.

The DTP vaccine given at the time of the study records has been replaced in the United States by a new vaccine called DTaP, which has fewer side effects. Children are usually given that vaccine in their first six months, with booster shots later on. Many pediatricians suggest giving children acetaminophen – such as Tylenol -- (not aspirin) after a DTP shot to control fever, thus reducing the risk of fever-related seizures. The MMR vaccine is typically given in two doses, one at age 12 to 15 months and a booster later on.

Kaiser Permanente is a group practice health care organization serving 445,000 people in Northwest Oregon and Southwest Washington, and some six million in California.

For more infomation contact:
Terry Fitzpatrick (503) 335-6602 or
Jim Gersbach (503) 813-4820

Released: August 29, 2001

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