Aston Villa loanee Kyle Walker pulled out to join the senior squad for their game with Denmark, while Manchester United's Chris Smalling, Manchester City's Micah Richards and Sunderland's Jordan Henderson have all picked up knocks.
Also out of the squad are West Ham's James Tomkins, Bolton's on-loan striker Daniel Sturridge, Arsenal full-back Kieran Gibbs and Villa midfielder Fabian Delph.
Howson has been joined by Chelsea's Josh McEachran, Barnsley's Kieran Tripper, Leicester loanee Kyle Naughton and Crystal Palace forward James Vaughan.