Doncaster and Bassetlaw Teaching Hospitals NHS Foundation Trust said the figure was the highest ‘in a few weeks.’
A spokesman said: “The number of patients with us with Covid has reached above 100 for the first time in a few weeks.
"Colleagues continue to do a fantastic job and are managing our position well, due to a combination of high vaccination rates and prior infection immunity.
"There’s no need for any alarm, however we just want to remind local people to wear a mask when coming to our sites for any appointments. Hopefully this figure will begin to fall in the next few days.”
It comes as people aged 75 and over and those clinincally vulnerable are invited for a booster jab, which will be the fourth dose of Covid vaccine for many.
A spokesman for Doncaster NHS said: “People aged 75 and over, and people aged 12 and over who are immunosuppressed, are now eligible for a Spring COVID-19 booster vaccine.
“The NHS will contact eligible people to book their next vital jab."
Visit nhs.uk/covid-booster for more information.
Covid rates have risen in Doncaster and across the country in recent weeks following the Government’s lifting of all remaining coronavirus restrictions including the need to legally self-isolate, even in the event of a positive test along with face masks no longer being mandatory in all settings.