Question

which statement best explains the why the influenza vaccine must be updated every year?
a. in some years, the influenza vaccine is not as strong as in others.
b. in some years, the influenza vaccine kills the virus, while in other years it does not.
c. the influenza virus adapts and mutates every year, so new vaccines must be produced.
d. the influenza vaccine does not necessarily stimulate the immune system to produce antigens.

Explanation:

The influenza virus is known for its high mutation rate. This means that the virus changes its genetic makeup over time. Vaccines work by targeting specific parts of the virus. When the virus mutates, those targeted parts can change. So, to effectively protect against the current - year's influenza virus, the vaccine needs to be updated.

• Option A: The strength of the vaccine is not the main reason for annual updates. Vaccines are formulated to a certain standard, and if there was a problem with strength, it would be a manufacturing or quality - control issue, not a reason for annual updates.
• Option B: Vaccines do not "kill" the virus. They prepare the immune system to recognize and fight the virus. This option has a fundamental misunderstanding of how vaccines work.
• Option C: Since the influenza virus mutates every year, the antigens (the parts of the virus that the immune system recognizes) change. So, new vaccines with the updated antigens (to match the current - year's virus) must be produced.
• Option D: Vaccines are designed to stimulate the immune system to produce antibodies (not antigens; antigens are on the virus or foreign substances). This option has a wrong biological concept.

Answer:

C. The influenza virus adapts and mutates every year, so new vaccines must be produced.