Multiple choice question Influenza is a virus that infects the cells of the respiratory tract and can cause fever, runny nose, headache, coughing, and muscle pain. Scientists develop new vaccines against the influenza virus every year. Why must scientists create new vaccines for this virus so often?
A. The virus fights off the vaccine and becomes resistant.
B. Different people respond to the vaccine differently.
C. The virus surface proteins mutate rapidly.
D. The vaccine is broken down by the immune system.