CDC provides the efficacy of its flu shots
Using the best cherry-picked study each year for the last 15 years
https://www.cdc.gov/flu/vaccines-work/effectiveness-studies.htm
CDC’s graphic designers also produced this beauty, but I have never seen convincing evidence that what they say is true.
CDC = Criminal Drug Cartel
The flu injections have been marvelous for me since I have avoided them all and haven't gotten the flu in over 25 years. See CDC, you are the most useless of agencies.