Flu vaccines for the 2019 to 2020 season

The composition of the 2019-2020 flu shot will be slightly different from last season's flu shot. Specifically, there will be a different strain of the H1N1 virus and a different strain of the H2N3 virus in this season's flu shot, compared with last season's shot. The 2019-2020 trivalent flu shot will contain the following strains of the flu virus:

• A/Brisbane/02/2018 (H1N1)pdm09-like virus — This is the H1N1 component that is different from last year's flu shot. 
  
• A/Kansas/14/2017 (H3N2)-like virus — This is the H3N2 component that is different from last year's flu shot. 
  
• B/Colorado/06/2017-like (Victoria lineage) virus — This is the influenza B strain component that is the same as last year's shot. 
  

The 2019-2020 quadrivalent vaccine will also contain a second influenza B strain called "B/Phuket/3073/2013-like (Yamagata lineage) virus," which was also included in last season's quadrivalent vaccine.