PEV makes its host stronger, smarter, faster, and helps them heal more quickly. Those two are Alma Lancaster (Lana Hale, my oc) and James Smith. This was used on a total of ten children, though all but two were in the graduating classes before 2282, which means that only two are alive and escaped being harvested.
Nothing worked until they combined the Pan-Immunity Virion and the Forced Evolutionary Virus, which resulted in PEV: the Pan-Immunity Evolutionary Virus. Pills, steroids, gene alteration and hand-picking specific genes to go into their DNA. Vault-Tec and the Institute tested a number of methods to make these children smarter and stronger. (So yes, they're all test tube babies.) The children were led to believe they'd be going to 'Uptopland,' aka the Commonwealth, and a 'good' harvest was considered 'only' 74% of the children failing to meet Vault-Tec's standards. Once the children hit 18, they were either incinerated or harvested to create more children from their genes. They're there to get the Institute's research back. This explains why, in-game, synths can spawn in Vault 75 and kill Gunners. Vault 75 was focusing on enhancing the human gene pool, and about 20-30 years ago they started collaborating with the Institute on their experiments.
