Jeffers butted the Vale captain Tommy Fraser and, after watching a DVD of the incident, the Owls manager Brian Laws said the forward's behaviour had been totally unacceptable. He has also been fined two weeks' wages.
"His conduct was totally unacceptable and something that this football club will not tolerate from any player," said Laws.
"We have therefore enforced the heaviest punishment available to the club with immediate effect and transfer-listed the player.
"The kind of behaviour enacted on Tuesday night is completely unacceptable and does not represent what Sheffield Wednesday stands for and clearly sets a bad example for the game of football.
"I would like to apologise to our fans and especially the fans that attended the game last night, some of whom face major sacrifices to attend games, and deserve to be proud of our players - they have obviously have been let down by this incident."