The prison director at HMP Lowdham Grange believes they have turned the tide after being hit with a steep rise in coronavirus cases.
Almost 1,400 people were tested for Covid-19 following an outbreak of the virus inside the male category B prison at the start of this month.
The people being tested included both staff members and inmates after 84 cases of coronavirus were confirmed inside the jail.
These positive tests were 63 prisoners and a further 21 staff.
As a result of the outbreak, all 875 male inmates received a Covid-19 test as well as the 500 staff who work there.
Prison bosses said since the start of the month there has been a "significant" decrease in cases of the virus.
Nine prisoners are currently positive, which includes one new positive case over the weekend and 14 current prison and healthcare staff remain positive.
Visits to the prison are still suspended.
Mark Hanson, Serco prison director at HMP Lowdham Grange, said: "We are cautiously optimistic that we are through the worst of the incidence of Covid-19 at the prison and that the measures that have been put in place are working.
"We are continuing to be extremely vigilant and careful and are working closely with the NHS and Public Health England.
"The measures that we have taken to manage the virus, including the suspension of visits, are being kept in place for the time being and will regularly reviewed."
