The Foxes can now relax in the knowledge that they will not face the drop this season, climbing four places to 11th after picking up a first win in six games overall.
Albion have now lost four games in a row and gone five without scoring for the first time in their history, meanwhile, again falling short in front of goal as they struggle over the finish line.
For the first time since joining the club in January 2015, a run spanning 86 games, influential midfielder Darren Fletcher was left out of Albion's starting lineup in one of three changes, while Craig Shakespeare brought in Shinji Okazaki for Leonardo Ulloa.
West Brom just about had the better of an opening 45 minutes that lacked any real quality until Vardy's opener, testing Kasper Schmeichel through a back-post header from Chris Brunt and a Nacer Chadli attempt from the edge of the box.
The two biggest talking points centered around referee Mark Clattenburg, officiating for the final time in the Premier League, as he showed yellows to Danny Drinkwater and Claudio Yacob when reaching into his back pocket would likely have been the right decision - particularly in the case of the former.
Drinkwater got some of the ball but followed through on Chadli, while Yacob needlessly caught Okazaki with a stray elbow soon after.
Just when the half looked to be heading for a goalless conclusion, Okazaki pounced when Albion gave the ball away cheaply in midfield and set Vardy free to do the rest.
The Englishman made no mistake up against Ben Foster, tucking the ball home for his third goal in his last three appearances at this ground and his eighth strike in 11 since Shakespeare took charge in February.
Albion striker Solomon Rondon, without a goal in 19 matches and the man at fault for Leicester's opener, glanced a corner narrowly over at the end of the first half and blasted right down the middle early in the second.
There was a more open feel to the game as Vardy burst down the left and sent in a teasing cross for Okazaki, which had a little too much on it for his teammate 10 yards out.
Craig Dawson, the scorer of two headed goals here against Arsenal earlier this month, then failed to convert when getting on the end of another left-sided corner as the hosts began to ask more questions.
Leicester were being given the chance to counter, almost adding a second through Riyad Mahrez after he stepped inside and blasted into the side-netting, while West Brom came close to a leveller when James Morrison diverted a James McClean cross down the middle.
Mahrez curled wide inside the last 10 minutes, with that proving to be the final meaningful act of the game as Albion lost for a third successive home game for the first time in a year.