Nigerian international Yakubu has been allowed to join Leicester on loan, leaving manager David Moyes to choose from Louis Saha, Jermaine Beckford, Victor Anichebe, Magaye Gueye and Vaughan in the central striking roles.
Vaughan, who has also had loan spells at Leicester City and Derby County, made his Toffees debut in April 2005, scoring in a 4-0 win over Crystal Palace.
Cardiff City and Hull City were linked with a move with the player at the end of last year.
Meanwhile, the agent for French striker Garra Dembele has told BBC Scotland that Celtic have tabled an offer for the 24-year-old.
Dembele has scored 27 goals for Bulgarian side Levski Sofia this season.
"I can confirm Celtic made an offer for Garra and he is very interested," said Christian Emille.
"There has also been interest from top clubs in England too.
"At the moment, Levski are weighing up all options, but the player himself would prefer a move to a club in the UK."
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