Influenza viruses constantly shapeshift to evade recognition by the immune system. This shapeshifting occurs in critical proteins like hemagglutinin (HA), which controls how the virus attaches to human cells before entering them. Influenza viruses can evade immunity in two major ways: through the gr adual accumulation of mutations that make HA harder for the immune system to recognize or through reassortment events that can introduce substantially different viral proteins and potentially lead to flu pandemics. To address this challenge, seasonal flu vaccines remain the primary approach because they can be developed to target the flu viruses circulating most predominantly in a given season. ...read more read less