A new study suggests in most cases where a child develops epilepsy following vaccination, the underlying cause is some genetic or structural defect and not the shot itself. “These results have significant added value in counseling of parents of children with vaccination-related first seizures, and they might help to support public faith in vaccination programs,” wrote the authors.

The News on Vaccines, Fevers, and Seizures

Up to five percent of all toddlers have at least one febrile seizure — spasms or jerky movements brought on by a fever and sometimes accompanied with a loss of consciousness. Needless to say, many parents are frightened to see their child experience a seizure and because of the resemblance to epilepsy, they fear long-lasting effects. This, though, is not the case, as children recover quickly and are healthy afterward with no lasting effects. Most febrile seizures occur between the ages of 6 months and 5 years, which happens to coincide with a good portion of the vaccination schedule. Because of this concurrence, anti-vaccination advocates suggest the early childhood shots may be the cause of these seizures, which in turn may lead to epilepsy and other illnesses.

In 2012, a large study conducted in Denmark found babies inoculated with a commonly used five-in-one vaccine face up to a six-fold increased risk of febrile seizures. (Fever is a common and well-known side effect of receiving a vaccination shot.) The study found the overall risk to be low and no increased risk of recurring seizures or other lasting ill effects such as epilepsy. Interestingly, out of nearly 400,000 children involved in the study, 7,811 children were diagnosed with febrile seizures before they were 18 months old and the vast majority of these seizures were related to fever from infections and not related to vaccines.

For the study, a team of Dutch scientists reviewed and analyzed the medical data of 990 children with seizures after vaccination in the first two years of life, reported to the National Institute for Public Health and Environment in the Netherlands in 1997 through 2006. Next, the researchers obtained follow-up data for the children who were subsequently diagnosed with epilepsy and had had seizure onset within either one day after receiving an inactivated vaccine or five to 12 days after receiving a live attenuated vaccine.

Of 26 children with epilepsy onset after vaccination, medical data was available for 23 of them: 12 had developed epileptic encephalopathy, eight had benign epilepsy, and three had encephalopathy before seizure onset. Investigating further, the researchers identified underlying causes, including Dravet syndrome and genetic mutations, in 15 of the children (65 percent). While some may say these numbers are far from reassuring — after all no underlying cause was found for one-third of all the children — the authors address this issue.

"Although no underlying cause was detected in one-third of children with epilepsy with vaccination-related onset, a genetic basis of epilepsy in these children is still possible: genetic analyses were incomplete, some children had positive family histories for seizures, and molecular defects underlying many genetically determined epilepsies have yet to be discovered," wrote the authors.

Source: Verbeek NE, Jansen FE, Vermeer-de Bondt P, et al. Etiologies for Seizures Around the Time of Vaccination. Pediatrics. 2014.