You can get vaccines from the 5 men that have immunity to MKV you know, you just need to extract the men immune system then multiple it easy af.
And fuck that MC just accept the reality okay?!?! Talking about morals and all but you just let humanity die you're despicable. I can understand if you just said I don't want to have sex and don't want to save humanity it will be fine, I don't have the problem if you said it..but no! You talk about morals and shit while you yourself is just the same, letting your species to extinct, and YES HUMAN IS ANIMAL there's no such thing as "Kingdom Homosapiens" homosapiens is classified as Kingdom Animalia so basically human is animal, human need sex, need food, need rest, those three things is the essential for animal and human is animal.