Fever-related seizures (febrile seizures) are pretty scary, and roughly one in 25 children will have one (or more) during their childhood, according to the NIH. Some studies have suggested that some of the older pertussis (whooping cough) vaccines might cause fevers in infants, thus increasing the risk of these febrile seizures. A team of Danish researchers looked at the newer combination vaccines currently in use to see if this risk was still there. In Denmark, the children have the vaccine at 3, 5 and 12 months.
The researchers followed 378,834 Danish children to see if the combination vaccine for diphtheria, tetanus, whooping cough (pertussis), polio and Haemophilus influenzae type 2 (DTap-IPV-Hib) did actually increase the risk of either epilepsy or febrile seizures.
There was a small increase in febrile seizures on the day of the first and second vaccination--9 babies had seizures on the day of the first shot and 12 on the day of the second shot. While this was 6-fold higher than expected on the first shot and four times higher on the second, considering the study looked at more than a third of a million babies--at less than four babies having seizures per 100,000 vaccinations, it is still a very small risk. The overall risk of febrile seizures within 7 days of the vaccine was no different than that in unvaccinated babies, and there was no link between the vaccine and epilepsy over the 7 years of the study.
"The good news of our paper is that we didn't find an increased risk of epilepsy," which is more serious than febrile seizures and may cause brain damage, Aarhus University's Yuelian Sun explained to Reuters. "The prognosis after febrile seizures is good," she told Reuters Health.
There is a lot of talk about the risk of vaccines, from brain damage to epilepsy, and from autism to immune disease. But the babies who had seizures on the day of vaccination may have been more prone to seizures than those who didn't. Furthermore, diseases like pertussis are more likely to cause long-term damage than a febrile seizure. Studies may help to dispel many of the myths and misapprehensions surrounding different vaccines, allowing parents and physicians to make science-based decisions based on science--rather than anecdote and rumor. They also may help authorities identify vaccines that do genuinely have side effects associated with them.