A study, published in JAMA of almost 400,000 children, showed that children had an increased risk of febrile seizures, a convulsion that occurs secondary to a rapid increase in body temperature on the day of the first and second vaccination, with the combined diphtheria-tetanus toxoids-acellular pertussis-inactivated poliovirus – Haemophilus influenzae type b (DTaP-IPV-Hib) vaccine. However, the overall risk was low, with researchers observing no higher risk of epilepsy in those who were vaccinated, compared with those who were not.
The article’s background information says:
“Studies have reported increased risks of febrile seizures shortly after administration of whole-cell pertussis vaccine, as would be expected since the whole-cell pertussis vaccine often causes fever. The acellular [may contain cellular material but does not contain complete cells] pertussis vaccine has replaced the whole-cell pertussis vaccine in most countries because the efficacy of the acellular vaccine is comparable with the whole-cell vaccine and it has substantially fewer adverse effects, including fever.”
It is not known if a higher risk of febrile seizures exists with the acellular pertussis vaccine. In January 1997, acellular pertussis vaccine was introduced in a combined vaccine in Denmark.
Yuelian Sun, Ph.D., of Aarhus University in Aarhus, Denmark, and his team assessed the risk of febrile seizures and epilepsy in 378,834 children born in Denmark – between January 2003 and December 2008 – after receiving the DTaP-IPV-Hib vaccination at 3, 5, and 12 months. Follow up ran until December 31, 2009. The researchers used the data to calculate the incidence rate of febrile seizures during from the day of vaccination to 7 days (0, 1-3, and 4-7 days), after each vaccination and of epilepsy after the first vaccination.
From the total of all children in the study, 7,811 (2.1%) were diagnosed with febrile seizures before 18 months, of which 17 were diagnosed within 0 to 7 days after the first vaccination, 32 within 0 to 7 days after the second vaccination, and 201 within 0 to 7 days after the third vaccination. The assessment suggested that there was no higher risk of children suffering febrile seizures during the 0 to 7 days after the 3 vaccinations, in comparison with a control group of children who were outside the 0 to 7 day window of vaccination.
In comparison with the control group, the findings did, however, reveal a higher risk of febrile seizures on the day of the first and second vaccination, yet not on the day of the third vaccination. On the day the children were vaccinated, 9 children suffered febrile seizures after the first, 12 after the second, and 27 children after the third vaccination.
The researchers write:
“Within 7 years of follow-up, 2,248 children were diagnosed with epilepsy, 131 unvaccinated children and 2,117 vaccinated children. Among 2,117 children diagnosed with epilepsy after vaccination, 813 were diagnosed between 3 and 15 months and 1,304 were diagnosed later in life, but only 2 children were diagnosed with epilepsy on the day of the first vaccination and 1 on the day of the second vaccination. Compared with the unvaccinated cohort, vaccinated children had a lower risk of epilepsy in the first 15 months of life but had a similar risk of epilepsy afterward.”
They conclude:
“Although the relative risks of febrile seizures on the day of the 2 DTaP-IPV-Hib vaccinations were increased, the absolute risk of febrile seizures after DTaP-IPV-Hib vaccination was very low, and the prognosis of febrile seizures occurring shortly after vaccination was similar to the prognosis of febrile seizures occurring outside the risk period of vaccination.”
Written by Petra Rattue