No Link Between Flu Vaccine and Epilepsy

H1N1 influenza vaccine Pandemrix is not associated with increase in seizures

(RxWiki News) Epileptics are often encouraged to receive flu vaccines because the risk of seizure increases when a patient has the flu. With more focus recently on vaccine safety and side effects, many are wondering if this preventative measure could actually make conditions worse.

A recent study looked at the risk of epileptic seizures after receiving the vaccine for the H1N1 flu. The study found no evidence of patients having more seizures after vaccination.

"Get a flu vaccination."

Lisen Arnheim-Dahlstrom, PhD, and colleagues from the Karolinska Institute in Stockholm, Sweden examined 373,398 people who received a version of the H1N1 vaccine, Pandemrix, in three counties in Sweden.

Pandemrix was developed by GlaxoSmithKline and began being distributed for the H1N1 flu in October 2009. It was one of four authorized vaccines used during the 2009 flu pandemic known as the swine flu.

The safety of Pandemrix drew attention when cases of narcolepsy occurred in children and teenagers after receiving the vaccine. In addition, the European Medicines Agency (EMA) received reports of epileptic seizures occurring after vaccination.

These reports made further investigation of the drug necessary.

The researchers were able to access records for the 373,398 through the Swedish vaccination register, a database of all vaccinations in Sweden. The patient’s unique personal identification number was then used to look up histories of epilepsy and antiepileptic drugs in other registries.

Within the study population, 7,787 people were considered epileptic during the year before the study and 356,611 were not.

Dr. Arnheim-Dahlstrom and team determined how many of the total study population experienced at least one epileptic seizure during the time period of 90 days before vaccination to 90 days after vaccination. During this 180 day period surrounding the vaccination, 859 people experienced epileptic seizures.

For those previously diagnosed with epilepsy, there was no increase in risk of seizures during the first week after vaccination. During this week, there was an insignificant decrease in risk of seizure for people without epilepsy.

From day 8 to day 30 after the vaccination, there was no increase in risk of seizure for those diagnosed with epilepsy. There was an insignificant increased risk of seizures in people without epilepsy during this time period.

These results dismiss safety concerns with Pandemrix for those with epilepsy.

The study was published in the British Medical Journal.

Funding was provided by a grant from GlaxoSmithKline Biologicals in Belgium. The researchers received unconditional grants from GlaxoSmithKline for the study.

No other conflicts of interest were reported.

Review Date: 
January 4, 2013