Vaccines and neurologic disease.

Vaccines have undoubtedly been a medical milestone, preventing immeasurable morbidity and mortality from infectious diseases worldwide. Modern vaccines have tremendously reduced the global impact of numerous infections; they have succeeded in eliminating smallpox completely. However, the nature by which vaccines confer their protection-by stimulation of the immune system-means that in rare cases, adverse often immunologically mediated events may occur following vaccination. Some of the most severe of these involve the nervous system. The author provides an overview of the mechanisms of vaccinology, and describes the various vaccines available for particular neurologic illnesses. Possible neurologic adverse events following vaccinations, and the possible mechanisms of these events, are also discussed. Finally, procedures in place to ensure vaccine safety are reviewed.