There have been 2,193 further confirmed cases of COVID-19 in Ireland.
There are 513 patients hospitalised with the virus, of which 97 are in ICU.
This is the first time since early March that Irish hospitals have had 500 or more COVID-19 patients.
HSE figures from Monday night show that University Hospital Limerick had the most COVID-19 patients (52) - followed by St James's in Dublin (39) and Galway University Hospital (37).
The figures also indicate the number of ICU patients has dropped slightly, from 99 reported on Monday.
The five-day moving average of cases has risen to 2,131.
Chief Medical Officer Dr Tony Holohan says a "substantial" number of hospitalised people are not fully vaccinated.
"I am increasingly worried about the rising incidence of the disease nationwide. Our primary focus now must be to protect the most vulnerable from COVID-19.
"We are seeing a continuing increase in hospitalisation and intensive care admissions - a substantial amount of whom are not fully vaccinated - placing our frontline healthcare services, including non-COVID care, under significant pressure.
"It is essential that we do everything we can to break the chains of transmission of the Delta variant, in the community, in the workplace and in our homes."
Dr Holohan adds: "If you experience symptoms of COVID-19, even if you are vaccinated, please stay at home, isolate from others and arrange a free test immediately.
"If you have not done so already, please choose to protect yourself by availing of your free COVID-19 vaccine which will significantly reduce your risk of severe illness if you contract the disease.
"The vaccine, our best defence against COVID-19, is not the only tool we have to drive down the spread of the disease.
"Please continue to regularly wash your hands, cover your coughs and sneezes, open windows and ensure spaces are well ventilated, wear masks on public transport, shops, indoor workplaces and crowded outdoor areas, and by keeping a safe 2m distance from others as much as possible."