Y/A Apocalypse/Post-Apocalyptic (disease/sickness) originally on Wattpad but later published

[Karis]

Hello! I read a book probably around 10 years ago if I had to guess on Wattpad. I remember finishing the first book and the author saying they were working on the second book but that the first one was supposed to get published. In this book, there is a FMC who is traveling with her younger sibling trying to find a place they heard about that was supposed to be safe. They have to take medication the help keep them from getting sick. I can’t remember if it was an injection they had to take or pills. As they travel they end up meeting the FMCs childhood friend (MMC) who I think had moved away? They start traveling together. Towards the end of the book I remember them getting robbed or something similar and their medicine gets stolen so they really have to find the safe area now. At the end of the book they do find it but they are all separated and it ends on a cliffhanger. I have tried googling this book and haven’t found anything so I’m hoping someone here can help me out. Maybe it did’t end up getting published and that’s why I can’t find it? If you have any ideas I’d love to know!