The correct answer is Karl will get sick and Jose will not this time, but neither will get this influenza again since they both will have acquired active immunity to it.
In the case of Jose artificially active immunity has been induced due to vaccination. A vaccine instigates a primary response against the antigen without resulting in any signs of the disease. On the other hand, Karl will acquire active immunity naturally in future, as when an individual get exposed to a live pathogen, he or she develops the disease, and turns immune as an outcome of the primary immune response.
Human encroachment that has greatly reduced the prairie dog populations.
