The Gloucester prop, sidelined since suffering a broken arm during the Zurich Premiership game against Bath in mid-February, is battling to play again this season.
Initial hopes were that he might have been available for Gloucester's appointment with Leeds but club medical staff have now told him the fracture has not fully healed.
Vickery requires at least another two to three weeks' recovery time and he will be assessed on a daily basis, building towards Gloucester's final Premiership fixtures of the campaign against Sale Sharks (April 15) and Saracens (April 30), plus any play-off matches.
Sir Clive Woodward is due to announce the Lions squad for this summer's New Zealand tour on Monday April 11 and Vickery is a leading selection candidate.
"It is frustrating, just like the entire season has been. But the arm has got to be ready for top-flight rugby," said Vickery.
"It has been six weeks since the Bath game, and I have just got to wait for it to heal.
"I want to be part of Gloucester's end of season and play a role in this season's climax, and I am doing everything I can to work on my fitness. A return for Gloucester is first and foremost in my mind."
Vickery was sidelined for several months last year while he recovered from back surgery.
He then a suffered a blow-out fracture to his eye-socket in a league game against Wasps, before sustaining his current injury problem a fortnight into England's RBS 6 Nations campaign.