The Department of Health and Social Care says it can't reveal how much it spends on healthcare at the prison - because the information is commercially sensitive.
A Freedom of Information request submitted to health bosses asked for the figure in April, along with how a tender process had been run and the name of the medical practice which successfully bid for the contract.
In its reply, published this week, the department says it can't make the figure public - saying it's not in the public interest to reveal how much it costs to treat prisoners being held at Jurby.
However the DHSC says only the Peel Medical Centre applied for the contract in February 2015.
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