Can someone explain ne the last part of this manga i am too dumb to understand it

So the vaccine that was injected to ji sung was not yet complete where those who are injected before didn't turn into zombie but in exchange they died cause of the side effects. Ji sung ended up in coma after the injection but in the end he woke up. Basically the vaccine worked on him.

Oooo thank you (⌒▽⌒)