They're tell you! https://www.cdc.gov/flu/about/season/vaccine-selection.htm https://www.cdc.gov/flu/about/season/vaccine-selection.htm Ars Technica also did

They're tell you! https://www.cdc.gov/flu/about/season/vaccine-selection.htm https://www.cdc.gov/flu/about/season/vaccine-selection.htm Ars Technica also did a nice breakdown (with many related Q&As) https://arstechnica.com/science/2017/12/this-years-flu-season-is-upon-us-and-it-looks-bad-heres-what-you-should-know/2/#h1 https://arstechnica.com/science/2017/12/this-years-flu-seaso...