A secondary immune response occurs when an antigen is encountered on a second occasion, due to exposure to a pathogen that previously caused infection. Which property of some viruses explains the lack of a secondary immune response?
A. Viruses fail to induce a primary response.
B. Viruses can have a high mutation rate.
C. B cells do not interact with viruses.
D. Antibodies cannot interact with viruses.

B

Explanation:

Our bodies can produce antibodies against viruses when they're in the interstitium before they invade our cells. They induce a complete primary response with memory cell production.

And the biggest evidence is that if a person gets chicken pox (Varcilla), it's not likely that they'll ever get it again.

Now why isn't that so for all viruses? Why is it that we keep getting flu?

Not all viruses are like the Varcilla with stable genetic makeup. Many viruses keep changing their antigens so that even if the immune system produced antibodies against a certain strain with a certain antigen, it won't recognize a different, mutated strain.

Viruses can evade our immunological memory in this way.