“An increased risk of narcolepsy was found following vaccination with Pandemrix, a monovalent 2009 H1N1 influenza vaccine that was used in several European countries during the H1N1 influenza pandemic. This risk was initially found in Finland, and then other European countries also detected an association.”

https://en.wikipedia.org/wiki/Pandemrix

https://www.cdc.gov/vaccinesafety/concerns/history/narcoleps...