More than 50 inmates and corrections staff have contracted COVID-19 in Victoria since the start of the pandemic.
Attorney-General Jill Hennessy has told a parliamentary inquiry 23 adult prisoners and six staff have tested positive.
"Two of the staff had not worked during the period in which they were potentially infectious and all prisoners have been isolated," she told the Public Accounts and Estimates Committee's COVID-19 Inquiry on Wednesday.
Another 19 juvenile inmates, five young people on community supervision orders and four prison staff had also tested positive.
Only one staff member worked while potentially infectious and Ms Hennessy maintains there was no "prisoner-prisoner transmission" in the youth justice system.
Ms Hennesssy said all new prisoners are tested and required to spend 14 days in protective quarantine.
Personal face-to-face visits to Victorian prisons have been suspended in order to reduce the risk of transmission, while staff and professional visitors are screened and temperature checked prior to entering a facility.
Australian Associated Press