February 27, 2018
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Epilepsy in children unrelated to pandemic flu vaccination

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Pandemic influenza vaccination is not associated with an increased risk of epilepsy in children, according to an analysis conducted on data collected during an H1N1 pandemic in Norway.

“We have previously shown that vaccination against pandemic influenza increased the risk of febrile seizures in children, although to a lower degree than influenza infection, and there have been concerns about an association with later epilepsy,” Siri E. Håberg, MD, PhD, from the Norwegian Institute of Public Health, Oslo, Norway, and colleagues wrote. “There has been increasing focus on the role of infections and immunologic factors, not only in febrile seizures, but also in the etiology of epilepsy.”

To examine whether vaccination during an influenza pandemic contributed to an increased risk of epilepsy in children, the researchers analyzed data collected between 2006 and 2014 in children younger than 18 years in Norway. Hazard ratios for epilepsy after influenza immunization were estimated using Cox regression models. Håberg and colleagues then conducted a self-controlled case series analysis to approximate the incidence rate of epilepsy after pandemic vaccination within specific risk periods.

October to December 2009 marked the main period of Norway’s influenza A H1N1 pandemic. On Oct. 1, 2009, 1,154,113 children younger than 18 years old resided within Norway, and 50.7% were immunized against influenza. The researchers observed an incidence rate of epilepsy of 6.09 per 10,000 person-years between October 2009 and 2014.

Vaccination did not increase the risk of epilepsy during this period (HR = 1.07; 95% CI, 0.94-1.23). After conducting a self-controlled case series analysis, the researchers confirmed that there was no relationship between immunization and later epilepsy.

“Concerns about the role of vaccines as a cause of neurologic and developmental disorders in children may reduce the willingness to participate in vaccination programs,” Håberg and colleagues wrote. “Low vaccination rates may have consequences for susceptible individuals with higher risk of influenza complications. It is therefore important to perform large population-based studies exploring the risk of neurologic conditions after vaccinations to address such concerns.”

“Our finding of no increased risk of epilepsy after influenza vaccination is reassuring,” they added. – by Katherine Bortz

Disclosures: The authors report no relevant financial disclosures.

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