ITA 
Unused vacation leave can be used to interrupt the illness protected period
“The employee on sick leave is entitled to apply for the accrued and unused vacation leave, for the purpose of interrupt the illness protected period, since there is no incompatibility between illness and vacation leave. However, this right does not imply an obligation for the employer to accept the request.
An executive (dirigente) who chooses not to use up holiday entitlement loses the right to indemnity in lieu of same
Court of Cassation with Judgement No. 15952 of June 8, 2021