3 reasons Yerema is a useless charecter who made things worse.

1: Yes she has the blood in her to make vaccines, but that doesnt make up for the fact shes a member of a survival-tough-battle ready tribe but she cant defend herself for s#it and just lays there getting beat on unless you intervene EVERYTIME THERE ARE NEARBY ENEMIES. At the very least she could have been given a hanbo or something.

2: she doesnt contribute anything interesting and has no skills. At the very least Jin can store your weapons, what does Yerema do...oh yeah nothing. Just because you have important blood doesnt mean you cant do anything else to help your group survive, especially in a zombie-infested area. And look at it, when shes first introduced you have to undergo one of the hardest parts of the game which is escorting her helpless ass through villages like shes the Dala-Lama yet after that for the rest of the game she just stands around with hardly any lines. Its as if paris hilton/nicole richie was the only member of your group with life saving blood so they act like their all high and mighty now and sit on their asses, would you want people like that in your group? not really. And even with her blood *spoilers* it doesnt do anything helpful either.

3: Her backstory doesnt make sense and she literally made things worse. 1st off she tells you she was a native to the tribe and left to go to school in the city to escape an abusive dad and likely a tribe thats ashamed of her, ok that makes sense in a way..what doesnt is WHY THE HELL SHE RETURNED TO IT and became a member again :/ And because she wouldnt let West take more life-saving blood from her and locked herself in a cage, that let the laboratory full of useful,helpful scientests get overrun and killed by infected. Im sorry but even if it was to save her life what was worth saving? Yerema's a member of a tribe who was already 96% dead and infected, everyone she knew before was now dead and there was literally nothing else she had going for her future...so giving up all her blood and not fighting back was prob the best/useful thing she could have accomplished XD

sorry for the rant But I hated Yerema and just wanted to point that out :p