Some 10,404 confirmed Covid-19 cases were reported on Sunday.
As of Sunday morning, 426 patients were in hospital with the virus – a rise of 48 from Christmas Day.
The number requiring ICU treatment increased from 87 to 91 in the same 24-hour period.
A further 10,404 confirmed cases of virus were reported in Ireland on Sunday.
A record 13,765 cases of the virus were notified on Christmas Day, up from the 11,182 announced on Friday.
The latest figures were outlined after chief medical officer Dr Tony Holohan urged people to reduce their contacts in response to the rising case numbers.
The Department of Health said “large volumes” of case numbers were anticipated over the coming period.
On Friday, around 83% of the reported cases were believed to be the Omicron variant.
Dr Holohan emphasised that Omicron was more transmissible than Delta and urged that everyone continued to reduce contacts and avoid crowded places as much as possible.
“We know that this variant is more transmissible than even the highly transmissible Delta variant,” he said.
“As such, please do not socialise or meet indoors with people from other households.”
Dr Holohan added: “Avoid crowded places including retail environments.
“Choose to shop online where possible, queue outside and leave any retail environment that does not feel safe and that is not adhering to the public health guidance – implementing social distancing measures and queuing system, limiting numbers in-store and staff wearing masks correctly (covering nose, mouth and chin).
“If you are yet to receive a booster dose of Covid-19 vaccine, then you should take every measure you can to protect yourself until you are eligible to receive it.
“This includes avoiding risky environments and keeping your contacts as low as possible.
“All of the available evidence indicates that a booster vaccine will offer good protection against infection with the Omicron variant.
“If you have travelled to Ireland from overseas it is important that you take an antigen test every day for five days.
“If anyone experiences any symptoms of Covid-19, however mild, then it is important to self-isolate and arrange a PCR test.
“Our test centres are very busy at the moment due to the high incidence of Covid-19 across the country, however, it is important that you continue to self-isolate until you receive the result of your PCR test and further information from the HSE.”