Barnsley’s latest infection rate per 100,000 residents is 2,125.2 - five times the figure at the start of December.
Cases have climbed in the last few weeks following the emergence of the Omicron variant, with the five worst-hit days since March 2020 coming in the last days of December.
On December 29, 951 people tested positive for the virus in Barnsley - 600 more than the highest figure before last month.
The spike has resulted in public health boss Julia Burrows to issue a warning to residents that figures will continue to go up.
She told the Chronicle: “In line with most other areas nationally, we have seen Covid-19 case rates rocket in Barnsley and are now at over 1,500 cases per 100,000 people.
“We expect this to continue to rise.
“This is pushing rates up in some of our most vulnerable people, including those over 50 and 60 years old.
“All across the country rates in these older ages continue to climb, with no obvious signs of slowing.
“Although the vaccine progress locally is extremely good, particularly in our older and more vulnerable residents, we expect there to be an increase in hospitalisations over the coming weeks, further reduction in the already fragile health and care workforce.
The town’s vaccine roll-out, which health bosses believe is the best way to stop the spread of the virus, has been in full swing for more than a year.
More than 186,000 people have had at least one dose, equating to 84.1 per cent of the town, almost 173,000 are double jabbed and more than 123,000 people have had boosters.
However, 45 per cent of people taking a PCR test - where a swab is taken to a lab - are receiving a positive result.
These figures are at their highest since the start of the pandemic in April 2020.
Ms Burrows added: “As there have been no changes to national restrictions, we need to continue with the behaviours we know can help reduce transmission and keep ourselves and those around us safe.
“Using face coverings, keeping a safe social distance, washing our hands frequently and socialising in small numbers and in well ventilated spaces.
“It’s also important to get vaccinated to make sure that if you do catch Covid-19, you have the best form of protection against it becoming serious.
“Please get your booster jab and if you have not had any vaccination yet, it’s not too late.