Generalized convulsive seizure as an adverse event following immunization: case definition and guidelines for data collection, analysis, and presentation

The diagnosis of generalized convulsive seizure is based on descriptive terms for clinical signs and symptoms and does not require knowledge of ictal pathophysiology or imply its etiology. Since generalized convulsive seizures following immunization are usually of short duration [1], the diagnosis is frequently based on the clinical history alone. Any occurrence of that generalized convulsive seizure in vaccine recipients should be compared to a control group, ideally by placebo-controlled, double-blinded, and randomized comparisons or against a background rate. Because the definition itself defines a clinical entity without inference of a causal relation to a given exposure, the time interval between immunization and onset of the event cannot be part of the definition itself, but should be assessed as described in the guidelines.