Pandemic influenza vaccination carries no increased epilepsy risk
There appears to be no association between pandemic influenza vaccination and the risk of epilepsy among children, according to a study, which suggests concerns about the vaccination may be unwarranted.
In a cohort of 1,145,546 children aged <18 years, 572,875 (50.7 percent) were vaccinated against pandemic influenza. A total of 3,628 new cases of epilepsy were documented over a period of 5 years, yielding an incidence rate of 6.09 per 10,000 person-years.
No increase in the risk of epilepsy was observed following vaccination (hazard ratio, 1.07; 95 percent CI, 0.94–1.23). Data from the self-controlled case series were consistent with the finding of a lack of association between vaccination and subsequent epilepsy.
Although unclear, potential biological mechanisms that could explain a connection between inflammatory mechanisms, seizures and epilepsy may involve proinflammatory cytokines, which have been shown to increase in relation to febrile seizures. [Brain Dev 2007;29:425-430]
Viral infections can induce neural inflammation and cytokine release. Additionally, infections, vaccines and fever may trigger seizures, and some individuals may be predisposed to developing epilepsy after febrile seizure episodes. [Arch Dis Child 2007;92:589-593; Epilepsy Curr 2015;15:335-337; Epilepsy Res 2013;105:158-163; J Infect 2012;64:520-524]
Researchers noted that concerns regarding the role of vaccines as cause of neurologic and developmental disorders in children appear to be a barrier to participating in vaccination programmes. This has important implications, as low vaccination rates may have consequences for susceptible individuals with higher risk of influenza complications.
While the finding of no increased epilepsy risk after influenza vaccination is reassuring, additional large population-based studies exploring the risk of neurologic conditions after vaccinations should be conducted to address such concerns, researchers said.