Vault-Tec's most notable product was the vault. Officially, the vaults were part of “Project Safehouse”, designed to protect the American population from nuclear holocaust. In actuality, they had a more sinister purpose, a project known as the “"Societal Preservation Program" The vaults could not possibly have saved the citizens of the United States from the ravages of a nuclear war or a viral pandemic. With a population of almost 400 million by 2077, the U.S. would have needed over 400,000 Vaults to protect every man, woman and child. Vault-Tec was commissioned by the American government to build only 122 such vaults...
There are more but max is 3, I am seeing if I can add more.
Update time span is diminishing :) I have more time now because its getting cold and it will soon be winter.