Convince your hypothetical humanities-major roommate of the following two things. (Be sure to explain the concepts of coevolution, herd immunity, and immunological memory (including the main cells involved) in the appropriate places.)
a) Why they should get a flu shot, how despite making them feel sick one year it didn't actually give them the flu, and why they should get it again every year.
b) Why they should get both doses of a COVID-19 vaccine even though they are in a low-risk group and unlikely to get very sick if infected.