The 82-year-old Indiana Jones legend was scheduled to take to the stage at the prestigious Hollywood ceremony on Sunday but has been forced to pull out after being diagnosed with the viral infection that causes a painful rash on the skin.
Ford is said to be "doing okay and resting", following the diagnosis.
The Shrinking actor was announced earlier this week as one of the presenters for the 97th Academy Awards alongside the likes of Robert Downey Jr, Gal Gadot and Zoe Saldana.
The Hollywood icon's career shows no signs of slowing down with roles in 1923 and Captain America: Brave New World putting him in the spotlight recently and he claims that he will only retire when people "forget" about him.
Quizzed on when he could walk away from acting by Entertainment Tonight, Ford replied: "When you forget my name."
Meanwhile, he displays his horseriding skills in the Western drama 1923 but insists his abilities aren't as impressive as they appear on screen.
"Maybe from a contemporary point of view, the horses represent something - some special skill or danger - but they really are not," he told People.
"I spent half an hour on a horse, and from a contemporary point of view, you look at that, and say, 'Whoa, people used to do that,' but it really is not that difficult."
However, his co-star Helen Mirren was astonished by his talent.
"Harrison says that because he's a great rider," she said.
"I was incredibly impressed, I have to say, with watching him gallop off across the Montana hillside."
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