Tournament organisers confirmed the turn-around on Wednesday, with Healy tweeting that he was "very happy" with the outcome.
"The player had argued, among other things, that extending the three-week suspension over four weekends was not permissible under the relevant regulations," a Six Nations statement confirmed.
"The independent Six Nations disciplinary appeal committee - chaired by Professor Lorne Crerar (Scotland), along with Antony Davies (England) and Rod McKenzie (Scotland) - upheld the appeal."
The ban was initially extended to factor in a period over which Ireland wouldn't have been playing in the tournament anyway.
Healy's ban is now set to expire at midnight on 3 March, ahead of the game against France at the Aviva stadium in Dublin on 9 March.
The news will be a welcome boost for Ireland coach Declan Kidney after two defeats in the opening three games of the tournament.