"Ghost: The Musical" is Harding's theatre debut, in which she plays Demi Moore's character Molly from the beloved 1990 movie opposite former "Hollyoaks" actor Andy Moss.
The 34-year-old actress was diagnosed with an upper respiratory tract infection and has been told to rest by her doctor, reported Female First.
"Sarah went to see the doctor today who diagnosed an upper respiratory tract infection. She's been really pushing herself over the past three weeks, rehearsing solidly for the show and making sure her performance is perfect.
This comes days after she performed the play at the New Wimbledon Theatre, where her act was heavily criticised.
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