The telekinetic two-year-old girl at the end of Carrie was taken by The Institute
At the end of Carrie, a woman is writes to one of her friends about her two-year-old daughter's telekinetic abilities, which her grandmother also had. This may have been a Sequel Hook, or something else, but it's worth mentioning given Stephen King's fondness for Canon Welding. There is also a good reason why she would not have been present in The Institute—Carrie takes place in the late 1970s, and The Institute is set in the 2010s, which means that if this girl was taken to The Institute, she almost certainly would not have still been alive by the time Luke Ellis got there. The Institute is affiliated with, or part of, The Shop
The Shop (official name "The Department of Scientific Intelligence") is a US Government agency that appears from time to time in King's work, usually getting involved in morally-ambiguous supernatural research. The activities of The Institute sound like exactly the sort of thing they would be behind.