Vunipola had been one of England's best players in the opening three games but was ruled out of the rest of the tournament with ankle ligament damage.
Morgan, who has been a mobile and effective replacement off the bench in his last six games, will start for the first time since he played in both test victories in Argentina in June.
Exeter flanker Tom Johnson comes into the replacements.
Two-times defending champions Wales, England, Ireland and France all have four points after winning two and losing one of their first three games.
England: 15-Mike Brown, 14-Jack Nowell, 13-Luther Burrell, 12-Billy Twelvetrees, 11-Jonny May, 10-Owen Farrell, 9-Danny Care; 8-Ben Morgan, 7-Chris Robshaw (captain), 6-Tom Wood, 5-Courtney Lawes, 4-Joe Launchbury, 3-David Wilson, 2-Dylan Hartley, 1-Joe Marler.
Replacements: 16-Tom Youngs, 17-Mako Vunipola, 18-Henry Thomas, 19-Dave Attwood, 20-Tom Johnson, 21-Lee Dickson, 22-George Ford, 23-Alex Goode
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