This has so much potential and then ends before you can have a full wank.
The entire game should be the prequel sequence with the game actually starting once you took the vaccine.
At that point you'd have to pretend to still be infected, try to not have to do fucked up shit (and probably failing), regularly take the vaccine until it starts losing effectiveness at which point you desperately need to make the new vaccine while trying to maintain your cover with then after far more interactions and investigation getting to the real culprit.
EDIT: just checked DLSite, they have the audacity to ask 10$ for something this short?
That makes me sad.