Vardy scored in the 67th and 74th minutes after Thorgan Hazard had given the German side the lead with a fine finish from distance early in the second half.
Nigerian international striker Iheanacho, who signed from Manchester City on Thursday for £25 million ($32.8 million), set up Vardy’s winner but was substituted with an injury shortly after.
Leicester manager Craig Shakespeare said it was just a precautionary move.
“Last thing he needed was another kick on it (his leg), so we played if safe,” said Shakespeare.
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