Study: Vaccines linked to seizures

BOSTON (AP) — Two widely used childhood vaccines occasionally trigger seizures but do not appear to cause any long-term disabilities, such as epilepsy or retardation, according to the biggest study of the subject.

The study looked at children who had received the DTP vaccine to prevent diphtheria, tetanus and pertussis and the MMR vaccine for measles, mumps and rubella. Both vaccines can cause fever, and fever in turn can lead to seizures.

The possibility of seizures is one of a variety of concerns that prompt some parents to oppose routine vaccinations, even though health experts argue that the benefit of preventing common childhood illnesses far outweighs any possible hazards.

Although doctors have long known that some childhood vaccines can trigger seizures, the latest study, based on 679,942 youngsters, was intended to see how often they occur as well as look for any lingering complications.

"Overall, it's very reassuring," said Dr. Robert T. Chen, director of vaccine safety at the Centers for Disease Control and Prevention, which sponsored the study.

The study found the risk of a so-called febrile seizure was six times higher than usual on the day of getting the DTP vaccine, and it was three times higher than usual eight to 14 days after getting the MMR vaccine. This translates into six to nine additional seizures for every 100,000 children getting the DTP shot and 25 to 34 for those getting MMR.

During follow-up, those who had the febrile seizures after vaccination were no more likely than usual to have additional seizures or mental or developmental problems.

Generally, doctors say seizures caused by fevers are less worrisome than those that strike without a fever. Several other studies have shown that youngsters who have had febrile seizures grow up to have normal intelligence and behavior. However, Chen said some have wondered whether such seizures are more ominous when triggered by vaccines.

"Any risk is not nice for parents to hear about, including me, who is the father of a 2-year-old, but it's a very small risk in light of what they prevent," said Dr. William E. Barlow of the Group Health Cooperative, a Seattle health maintenance organization. Barlow was co-director of the study, published in Thursday's New England Journal of Medicine.

The study began in 1991 and followed children at four West Coast HMOs for seven years. Since then, the DTP vaccine has been replaced by one that is only half as likely to cause fever.

"These data demonstrate very clearly there is no increased risk of long-term effects from the febrile seizures that some children have following vaccination. Parents should be reassured," said Dr. Neal Halsey, head of the Institute for Vaccine Safety at Johns Hopkins University.

In April, an Institute of Medicine committee issued a report saying there is no evidence that MMR causes autism, as some have speculated.

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