Fevers leading to seizures, or febrile seizures, are terrifying to the parents and as per a new study, these seizures are somehow linked to certain vaccinations administered in childhood. Researchers from Denmark have shown that a combination of vaccines that protect against diseases, like diphtheria, tetanus, pertusis, polio and haemophilus flu type B (DTaP-IPV-Hib), increases the risk of febrile seizures on the day they get the shot. The risk is more on either of the first two doses of the combination vaccines. The study also shows that the overall risk of these seizures linked to vaccinations to be very low.
The study was conducted on 400,000 children and the results published in the Journal of American Medical Association. Researchers reported that the number of children with febrile seizures within the first week of the first dose as 17, the second dose as 32, and the third dose as 201. A total of 7,811 children were diagnosed with febrile seizures before they turned 18-months-old. Many of them were not related to vaccinations. In most cases, seizures were due to fever from infections.
Comparison of the data related to seizures due to other causes with those that happened within a few days of getting the shots, combination vaccination was found to increase the risk of febrile seizures. The increase in risk was seen mostly in very young babies. The vaccinations increased the risk six times on the first dose while the risk was nearly four times on the second dose. The overall risk associated with vaccination was very low, of the order of four per 100,000 vaccinations. There was no increased risk of epilepsy or repeat febrile seizures.
According to Nicola P. Klein, MD, PhD, a pediatrician who co-directs the Vaccine Study Center at Kaiser Permanente Northern California in Oakland, the result does not come as a surprise. For a long time it has been known that vaccines are associated with increased risk of febrile seizures. These seizures do not have very lasting effect and resolves on its own. The study has shown that vaccines do not increase the risk of epilepsy, she adds.
Another study conducted in US in 2010 and published in Pediatrics, did not find any increased risk with diphtheria-tetanus-pertussis (DTaP) part of the vaccine. The reason for this may be that the study did not distinguish between the seizures caused by other reasons and those caused by vaccinations. Because of this the slight increase in risk would have been missed. Another reason for the difference in the results of the two studies would have been the difference in the vaccines used in Denmark and US. But Yuelian Sun, PhD, an epidemiologist with the Department of Public Health at Aarhus University in Denmark, does not agree with this reasoning. According to him subtle differences in the components of the vaccine cannot cause a major difference in the results.