Neurologic Safety Monitoring of COVID-19 Vaccines: Lessons From the Past to Inform the Present.

The spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has triggered a global effort to rapidly develop and deploy effective and safe coronavirus disease 2019 (COVID-19) vaccinations. Vaccination has been one of the most effective medical interventions in human history, although potential safety risks of novel vaccines must be monitored, identified, and quantified. Adverse events must be carefully assessed to define whether they are causally associated with vaccination or coincidence.

Cerebral infarction due to smoker's polycythemia.

A 65-year-old man presented with fluctuating focal neurological deficits and neuroimaging findings of multiple small cerebral infarctions. His medical investigation revealed a >100 pack/year smoking history, and a haematocrit >60. Subsequent investigations led to a diagnosis of cerebral infarction due to smoker's polycythemia, the third such case reported in the medical literature.