Shadab was diagnosed with "high grade full thickness tear to the Rectus Femoris muscle", an injury he had sustained during his side's four wickets victory over New Zealand in the Napier T20I earlier this week.
As Shadab is not available for, at least, the Boxing Day Test, the team management has included left-arm spinner Zafar Gohar as a reinforcement.
Vaughan's comment came after Shadab was replaced by Fawad Alam for the second Test against England at the Ageas Bowl in Southampton.
Pakistan's tour of England begins on July 30 with a three-match Test series. This will be followed by a three-match T20I series from August 29 to September 2.
The results have hence put their participation in the impending England tour in doubt.
Several counties such as Yorkshire, Kent, Lancashire, Gloucestershire and Hampshire were forced to cancel contracts of their overseas players, including Indian cricketers Cheteshwar Pujara and R Ashwin.