The Health Service Executive has warned that contact tracers are receiving a "hostile" reception from some people deemed close contacts of a positive case of Covid-19.
"Calls have increased significantly in complexity and are taking longer," the HSE told RTÉ's Prime Time programme.
"The response from some people can be hostile as they are not happy to be identified as a close contact, and informed that they must restrict their movements."
Close contacts are advised to isolate for 14 days and to undertake two separate tests for Covid-19. The time it takes to trace such contacts has almost doubled since schools returned.
"Our turnaround time for contact tracing was 1-1.2 days until the return of schools. Since the schools returned the turnaround time has moved to closer to two days," the HSE said.
280 contact tracers made more than 10,000 calls last week and recruitment is under way to bring the total number of tracers to 500. But some cases are experiencing lengthy delays.
Grainne Myers told Prime Time that although she tested positive for Covid-19 on Saturday she was only asked to supply her close contacts on Wednesday. In the meantime Grainne advised people she believed would be close contacts that they should restrict their movements.
"You're really left behind once you get your test. I didn't really know what to tell people, all I could say was what I read online.
"My family hasn't been tested and they can't get a test unless they get contacted by the HSE," she explained.
"I was told my records were lost and they have no record of me being positive at all."
Grainne's friend Jen Keane was staying at home and waiting to be called by contact tracers.
"I have my phone in my hand 24 hours, waiting for this call," she explained.
"You can't get a test even if you know that you need one, there's nothing you can do. You have to wait for the wheels to turn and in our case the wheels aren't turning.
"[Contact tracing] is obviously not as resourced as it needs to be which is worrying because until we have a vaccine testing and tracing is all we have. I thought it was better than this," Jen said.
A number of hours after speaking to the programme Jen was called by contact tracers and referred for testing - five days after Grainne received her positive result.
In response the HSE said there will "unfortunately be people who are not contact traced quickly," and "when it happens efforts are made to investigate to improve the quality of the system.
"The ECDC recognise that contact tracing will never be 100%."
Most people now have more than six close contacts and in a school setting the average figure is 30 close contacts.
"The aim is to complete all three contact tracing calls within 1-1.5 days. There is a 12 hour window where no calls can be made (8pm-8am) and it is dependent on people answering our calls," the HSE told the programme.
There is also increasing concern over the number of people who are not attending for Covid-19 tests.
Close contacts are referred for two tests - one on day zero, which is the date they are identified as a contact, and again seven days after they were in contact with the confirmed case.
Latest figures show that while 91% of close contacts attend the first swab, just 65% of people are undergoing the follow-up test.