The Leicester number eight joined the squad in New Zealand on Sunday as cover for Nick Easter but has now been officially inducted into the squad.
Prop Sheridan's tournament ended in England's opening victory over Argentina when he suffered a shoulder injury.
Easter has been suffering with back problems, while Matt Stevens has ankle problems, so Johnson has made the decision to call-up the 28-year-old.
"Nick is making good progress as is Matt Stevens, but with Thomas now out here it makes sense to get him into the squad officially so he can join in with training," said Johnson.
"We also owe it to Leicester to make a decision so that they can plan accordingly without him."
England next take on Scotland on Saturday.