Here, I give a brief overview of the history and nature of influenza viruses, including why it has been so difficult to develop successful vaccines. First, all influenza viruses have single stranded, negative-sense RNA. The HA and NA surface proteins are recognized by our immune system as foreign substances —known as antigens. But sometimes a single cell —whether human or avian or porcine— can become infected by two different influenza A viruses at the same time. The challenge: any universal influenza A vaccine has to successfully account for both antigenic drift and antigenic shift.
Source: Forbes August 13, 2022 00:39 UTC