Cataclysm

(This was actually inspired by a dream I had a few days ago, and I thought it would make a great story. I don't know of you'll think it's good or not, and I might make some grammar mistakes. So feel free to correct me, but please don't comment anything rude or hateful. Enjoy!)

A scientist was doing researches on Gene mutation to improve the human population's immune system. But one night when he thought he had succeeded, what he had found was not really what he thought it would be. This was far worse.

A vaccine has been going wild these days. Supposedly it improves the human immune system? Everybody's getting it for some reason. At least that's what Harper thought about it. She's in her second year of highschool right now. Everone goes crazy about anything that's going viral. That's what people do anyway. Try to catch up to the newest style, the newest trend, the newest anything. She's glad she doesn't care about those things. Isn't it stressful trying to catch up to all those styles or whatever? Yeah, she'll pass. She's healthy enough anyway.

What happens if she starts to notice people around her started acting weird, not like their selves?