The operations of 75 care homes are at "significant risk" and have a 'status red' rating due to staffing problem.
Care homes, particularly those for the elderly, are at the frontline of the fight against Covid-19 with a large proportion of deaths occurring among vulnerable residents in private and public facilities.
It emerged at the weekend that 21 people have died in one care home alone - St Mary's Hospital in Dublin's Phoenix Park.
Serious questions have been raised about the priority given to supporting nursing homes in the early days of the emergency.
Some nursing homes have also seen a staffing crisis as workers either fall ill with the virus or have to self-isolate because they have been in contact with a suspected case.
The HSE last night defended its response as it revealed that 75 care homes had been given a 'red' rating using the traffic light system of assessing long-term residential care facilities in receipt of additional support.
There are 425 homes getting some level of help, ranging from infection control advice to extra staff and deliveries of personal protective equipment (PPE). HSE chief operations officer Anne O'Connor said that 221 of these were deemed stable after some intervention and had been categorised as 'green'. Another 129 continue to need "significant enhanced supports".
And 75 are in the 'red' category where there is a "significant risk in terms of operation".
Of those in the most at-risk category, 17 are HSE-run facilities. Ms O'Connor said the 75 homes were "particularly challenged" in terms of having enough staff.
She said 119 of the HSE's community staff and approximately 100 acute staff had been deployed by the HSE to care homes as "boots on the ground".
These deployments have been weighted towards the homes whose operations have been most at risk.
Ms O'Connor also warned that as coronavirus testing was ramped up in care homes, it was inevitable that more outbreaks would be identified.
She said the challenge for the HSE was to identify the nursing homes "that have a critical need for a high level of support".
Ms O'Connor said nursing homes had been prioritised for deliveries of PPE and accounted for 60pc of supplies provided by the HSE over the past week.
She insisted the supply of PPE to nursing homes was "very, very significant".
HSE chief executive Paul Reid said the number of staff redeployed on its own did not reflect the scale of the HSE's support for nursing homes in terms of resources.
He gave the example of a home in Co Louth that has been "practically taken over" by the HSE and pointed to the support provided by multi-disciplinary teams of health professionals.
"If you were to calculate the total resource committed to private nursing homes it would be very significant," he said.
Mr Reid also revealed the HSE planned to almost double its already massively increased spend on PPE and hoped some of this can be provided by domestic suppliers.
The annual spend on PPE before coronavirus was €15m. The HSE has already ordered €208m in additional equipment from China and it is probably going to order another €150m-€200m worth of PPE.
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