Unlike most other vaccinations, the one for influenza needs to be take every year in order for it to be effective. This infographic answers the question Why? It talks about antigens and receptors so isn't pitching itself to the 5-sec-glance audience but to those with the curiosity (and need) to understand why this is the case.
Would you be interested in translating or adapting it for your own use?
We have adaptable files (Adobe Illustrator) available for exactly that purpose.
Contact Health.Communication@ecdc.europa.eu to get those files or to find out more.