Final answer:
It leads to changes in the antigens, the molecules that trigger the immune response. Therefore,the correct Option is Option a. Antigenic drift.
Step-by-step explanation:
Antigenic drift refers to the gradual accumulation of mutations in the genes that code for surface proteins of the influenza virus, particularly the hemagglutinin (HA) and neuraminidase (NA) proteins. These mutations cause subtle alterations in the viral surface proteins, impacting the recognition and binding of antibodies. As a result, the immune system's response to the virus becomes less effective over time, allowing the virus to evade immunity established from previous exposures or vaccinations.
This process is a continuous, ongoing mechanism observed in seasonal flu viruses, leading to the need for updated influenza vaccines periodically to match the circulating strains. Antigenic drift does not result in entirely new viral subtypes but rather small changes within existing subtypes, contributing to the persistence of seasonal influenza. It's distinct from antigenic shift, which involves major genetic reassortment leading to the emergence of entirely new viral strains with novel HA and/or NA proteins, often causing more severe pandemics.
Understanding the concept of antigenic drift helps public health officials and researchers predict and prepare for changes in circulating influenza strains, aiding in the development of effective vaccines to combat evolving viral variations.
Therefore,the correct Option is Option a. Antigenic drift.