Influenza A virus subtype H3N2 (A/H3N2) is a subtype of viruses that causes influenza (flu). H3N2 viruses can infect birds and mammals. In birds, humans, and pigs, the virus has mutated into many strains. In years in which H3N2 is the predominant strain, there are more hospitalizations.
Quadrivalent influenza vaccine adds
A/Brisbane/02/2018 (H1N1)pdm09-like virus
A/SouthAustralia/34/2019 (H3N2)-like virus
B/Washington/02/2019-like virus [B/Victoria lineage]
B/Phuket/3073/2013-like virus [B/Yamagata lineage]