Vault 22 was designed to be an experiment on self-sufficiency, with a focus on plants keeping the facility’s population alive. However, while initially successful, there were some gruesome side effects that later marked the vault as a place to avoid at all costs.
The plants released fungus spores, which infected many of the inhabitants. This led to the fungus taking over the body, killing the host and becoming a deadly, humanoid creature called a Spore Carrier. These Spore Carriers initially appeared as normal humans, who would walk around spraying spores and infecting further victims. However, they soon took on a more plant-like appearance, with a ferocity matching that of the feral ghouls. Vault 22 was all but abandoned by the remaining survivors, and the vault is surrounded by dozens of warning messages.
Horrifically, the player can come across a number of very small Spore Carriers, suggesting that many of the victims were babies and infants.