Flu Shot Not Associated With Increased Risk of Pediatric Epilepsy

Concerns about influenza vaccination causing epilepsy in children appears to be unwarranted.

Seizures, including febrile seizures, are the most commonly reported neurologic complication of influenza infection.

And, influenza vaccinations have also been associated with an increased risk of febrile seizures in children.

But, the results from a new study showed the H1N1 vaccination was not associated with an increased risk of epilepsy in children.

In this study, researchers investigated the possible association between epilepsy and the H1N1 pandemic influenza vaccine administered among children aged 0 to 17 years, in Norway during 2009.

One limitation of this study was that it did not account for pre-existing comorbid conditions, which may have predisposed participants to epilepsy and increased their likelihood of being vaccinated.

This research focused on 1,154,113 children in Norway, less than 18 years of age. Of these children, 50.7 percent were vaccinated against pandemic influenza.

From October 2009 through 2014 there were just 3,628 new cases of epilepsy reported, with an incidence rate of 6.09 per 10,000 person-years.

Which means, the risk of epilepsy was not increased after the pandemic flu vaccination (hazard ratio: 1.07; 95% confidence interval: 0.94–1.23.)

Childhood epilepsy has many different causes, but in most cases, the causal mechanisms are not identified, reports the Centers for Disease Control and Prevention (CDC). 

Several studies of children in the United States have been conducted to see if there is an increased risk for febrile seizures following flu vaccination.

• Flu vaccine was not found to be associated with febrile seizures in one study that looked at 45,000 children aged 6 months through 23 months of age who received a flu vaccine from 1991 through 2003 
• Seasonal flu vaccine and the 2009 H1N1 flu vaccine were not found to be associated with febrile seizures in children during the 2009-10 flu season
• Some studies have detected a small increased risk of febrile seizures in young children following the flu shot in some flu seasons. In these studies, the risk of febrile seizures was increased for children 12 through 23 months of age, particularly when the flu shot was given at the same time as the pneumococcal conjugate vaccine (PCV13) and diphtheria, tetanus, and pertussis (DTaP)-containing vaccine.

However, there is a clear link between febrile seizures, particularly complex febrile seizures, and increased risk of later epilepsy.

Increased seizure risk has been described after administration of other vaccines, but the association with later epilepsy is less clear.

In several studies, researchers conclude that pandemic vaccination may influence the risk of other neurologic conditions, such as Guillain-Barré syndrome, encephalopathies, and narcolepsy, suggesting there is a potential influence on the brain when the immune system has been triggered by vaccination.

However, no association with narcolepsy was found in a study of a non-adjuvanted pandemic influenza vaccine used in the United States.

This study was supported by the Norwegian Research Council grant 201919. These researchers did not disclose any conflicts of interest: Siri E. Håberg, Kari M. Aaberg, Pål Surén, Lill Trogstad, Sara Ghaderi, Camilla Stoltenberg, Per Magnus, Inger Johanne Bakken.