HSE Chief Executive HSE Paul Reid has said work is under way to increase capacity for Covid-19 PCR tests.

Online self-referral appointments were not available in a number of counties again today - as demand for testing continues to rise.

This evening, the HSE's online portal showed there were no Covid-19 PCR tests available in 23 counties.

The only counties offering appointments are Donegal, Mayo and Roscommon, which had 752, 524 and 197 respectively.

Deputy Chief Medical Officer Dr Ronan Glynn has appealed to anyone with symptoms to restrict their movements while waiting for a PCR test - and not to use an antigen test.

He said he fully appreciates the frustrations people are feeling around the lack of availability of Covid-19 PCR tests.

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He agreed that the shortage of testing is causing problems but said it is "impossible" to ramp up testing to the scale that would be required to test everyone within a day or two.

He told RTÉ's Today With Claire Byrne show that between 500,000 and 700,000 people last week had cold or flu-like symptoms. There was "no testing system in the world that can ramp up testing to 20% of its population in a week-on-week basis," he said.

Dr Glynn said that the core message is for people to isolate as soon as they develop symptoms.

He advised that even those people who get a negative PCR test should isolate as long as they have cold or flu-like symptoms, adding that anyone unvaccinated, of any age, needs to restrict their movements if someone else in their household has symptoms.

Earlier, the HSE's lead for the test and trace programme said that despite providing over 200,000 PCR tests in the last week, there is pressure to try to meet the demand for timely PCR tests nationwide.

Damien McCallion said that one million people have had PCR tests in the last six to seven weeks, and while laboratories are working well, the pressure is being felt at swab centres.

Speaking on RTÉ's Morning Ireland, he said that testing capacity has been ramped-up with the help of the private sector and the Defence Forces.

Additional centres have opened in Dublin, Cork and Limerick in recent days and more are planned.

He said the country is in a wave with significant demand and "hitting levels none of us thought we would ever hit".

PCR tests are being prioritised for acute hospitals, clinical referrals and contact tracing.

Mr McCallion said the HSE is working to try to increase capacity for PCR testing, but "there are limitations we will hit".

He said that ongoing recruitment is happening, but that "no one test is a silver bullet, it is a combination of measures".

The Minister for Foreign Affairs said the system is "not perfect" as he appealed for patience and cooperation from people awaiting PCR tests.

On RTÉ's News at One, Simon Coveney said that despite 25,000 tests being carried out each day, there are pressure points in some areas.

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Health Service Executive CEO Paul Reid said 210,000 PCR lab tests have been completed in the past week.

"I fully acknowledge our staff are exhausted, they are frustrated, they are tired", Mr Reid told the Oireachtas Joint Committee on Health.

He said 82% of those tested will get results within 24 hours, but he acknowledged there are delays.

"It is really important that people who feel they need a PCR test ... do restrict their movements for at least 48 hours" after symptoms abate, Mr Reid added.

Mr Reid said that "the entire health system is now under very serious pressure", adding that the latest Covid surge will "place even more pressure on staff" with "a huge demand" being made of staff and resources.

As of this morning, over 630,000 booster vaccines had been administered, with 72,000 of those given to immunocompromised people.

Rise in cancellation of elective surgeries

Mr Reid also told the committee that around 1,000 elective surgeries have been cancelled in the past month.

He said that "we are still making reasonable progress" in addressing the cancellation of elective surgeries.

There were 180 cancellations per week in September, which rose to 350 a week in October.

Mr Reid said the HSE had overseen a net increase of consultants of 333 since January 2020.

He was responding to Sinn Féin's David Cullinane, who also asked about the number of antigen tests available.

Mr Reid said the HSE has a "drawdown contract" and has two million antigen tests, and can access "at least ten million" more and "can extend that further".

"Stock is not the factor," he stated.