Fever Seizure Risk Low After Vaccination

Pertussis vaccine currently used has very low rate of severe fever and no risk for epilepsy

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(RxWiki News) Parents concerned about multiple-vaccine shots can rest easier knowing shows one common combination shot is as safe as single vaccines and safer than skipping the vaccine altogether.

Doctors have known there is an association between the previously used whole-cell pertussis vaccine and extremely high fevers resulting in a seizure.

But they didn't know if the the currently used acellular pertussis vaccine might lead to a higher risk of these febrile seizures. A new study shows it doesn't.

"Vaccinate your child according to the CDC schedule."

Yuelian Sun, Ph.D., of the Department of Public Health at Aarhus University in Denmark, led the cohort study of 378,834 children born between January 1, 2003 and December 31, 2008.

The difference between the two vaccines is that the acellular one lacks a complete cell of the pertussis vaccine, instead having only a few pieces of it to evoke an immune response.

Today, the acellular vaccine is given with diphtheria and tetanus vaccines in the DTaP shot. In countries such as Denmark, where this study was done, it's given in a combined shot with diphtheria, tetanus, polio and Hib.

For this study, Sun's team examined whether children had a febrile seizure within a week after each vaccination at children's 3-month, 5-month and 12-month check-ups.

They also looked at how many children were diagnosed with epilepsy in the group to determine whether any association existed between epilepsy and the immunizations.

They found the rate of febrile seizures within a week of vaccination was less than 4 cases per 100,000 shots administered, and the children experiencing them had no higher risk of long-term problems.

Of the total group, only 17 babies, or less than 0.005 percent, had a febrile seizure within 0 to 7 days after their first vaccination. Following the second and third vaccinations, 32 children (0.008%) and 201 children (0.05%), respectively, experienced a febrile seizure within the next seven days.

Compared to a demographically similar group of unvaccinated children in the general population (the reference cohort), the children receiving the vaccines did not have a higher risk of having a febrile seizure overall across their first year.

However, they did have a slightly higher risk of high fever leading to seizure on the days of the first (3-month) and second (5-month) immunizations.

Compared to the reference group, the children vaccinated with the DTaP-IPV-Hib shots had a 40 percent lower risk of epilepsy diagnosis between 3 and 15 months, but their risks evened out to be the same for epilepsy occurring later in life in both groups.

The researchers controlled for birthday, gender, gestational age, birth weight, mother's education and income, and parental history of epilepsy. They were not able to isolate which component in the combination vaccine might increase a risk of febrile seizures.

The study appeared online in February in JAMA. It was funded by grants from the Lundbeck Foundation, the Danish Medical Research Council, NordForsk and Seventh Framework Programme from the European Research Council. The authors reported no conflicts of interest.

Last Updated:
February 23, 2012