New flu shots are needed every year to protect against infection because of __________.

• A. latency
• B. expiration
• C. a direct attack on the immune system
• D. None of the listed reasons is correct.
• E. antigenic variation

Answer: (E)

Verified step by step guidance

1. Understand the concept of antigenic variation: Antigenic variation refers to the process by which pathogens alter their surface proteins to evade detection by the host's immune system. This is a common strategy used by viruses, including the influenza virus, to avoid being targeted by antibodies produced from previous infections or vaccinations.
2. Recognize the role of antigenic variation in influenza: The influenza virus undergoes frequent changes in its antigens, specifically the hemagglutinin and neuraminidase proteins on its surface. These changes can be minor (antigenic drift) or major (antigenic shift), leading to new strains of the virus that the immune system may not recognize.
3. Understand why new flu shots are needed annually: Due to antigenic variation, the influenza virus can change significantly from one year to the next. This means that the immune response generated by last year's flu shot may not be effective against this year's virus strain, necessitating the development of a new vaccine each year.
4. Differentiate antigenic variation from other concepts: Latency refers to a period when a virus is present in the body but not actively causing symptoms. Expiration is not relevant to the need for new flu shots. A direct attack on the immune system is more characteristic of viruses like HIV, which specifically target immune cells.
5. Conclude with the importance of vaccination: Annual flu vaccinations are crucial for public health as they are designed to protect against the most prevalent and anticipated strains of the influenza virus, taking into account the antigenic variations that occur.