It simply comes down to the situation and a vaccine is basically pointless in a zombie outbreak
The walkers are dead bodies all this vaccine would do is make young children (which you are probably never going to meet) from a possible infection (which is an unlikely cause of death) when a walker could still rip them apart or they could be shot or starve to death
It is a useless vaccine which would never be used
But if it was literally a button that ended the zombie outbreak I would choose it over Clem...
I choose Mankind I just wouldn't in this unbelievable pointless situation