I've noticed that the lyrics include "Bring me 115" while being sung by Raspier, Zombie like sounding singer.
And i thought to myself, maybe its a clue.
So if the Zombie is saying bring me 115 could it be of some importance to the zombies, like for example:
-Could it also be the cure to those effected by Nova 6? It has the abillity to re-animate dead cells,which is what created the zombies, and what would it do to already alive cells?
-Could it be for the zombies to become more powerful? Maybe 115 has the effect of mutating the already re-animated cells and making them become increased in strenght?
-If it is actually the older version of Sam singing "Bring me 115" maybe shes implying that she needs to be re-animated to stop the zombies?
Theres other possible reasons, but these 3 seem the most plausable to me.