What is the name of the phenomenon that explains why a new flu vaccine must be created every year?

A) antigenic drift
B) antigenic shift
C) resistance
D) virulence

Antigenic Drift

Describes natural selection on seasonal influenza viruses that alters the structure of surface proteins, allowing them to evade the antibody-mediated immunity induced during previous infections or vaccinations.

Flu Vaccine

A vaccination that protects against the influenza virus, redeveloped each year to combat the seasonally evolving strains.

Resistance

Resistance refers to the capacity of pathogens to defend against antibiotics or other drugs.