Adverse neurologic reactions after both doses of pandemic H1N1 influenza vaccine with optic neuritis and demyelination.

When a neurologic condition develops after vaccination of a patient, the causal relationship is difficult to determine. We report an unusual case in which neurologic signs occurred in a previously healthy child after both doses of H1N1 2009 influenza vaccine, culminating in bilateral optic neuritis and disseminated encephalomyelitis. A causal association is more likely with repeated injury following influenza vaccination.