The HSE has said the recruitment process has delayed building up capacity for testing and tracing in the summer at an Oireachtas Committee.
Representatives of the HSE apologised for the situation which resulted in almost 2,000 people having to carry out their contact tracing after testing positive with Covid-19.
The committee was told there is almost 600 people currently working on contact tracing, with a further 800 staff to be recruited in the coming weeks. That 800-strong cohort includes replacements for HSE and other public service staff who are currently involved in contact tracing but will be returning to their old roles, though.
Sinn Féin's health spokesperson David Cullinane repeatedly questioned why recruitment was not expedited in the summer when the country had low numbers of cases.
"We're now being told that 60, or 70, staff would be recruited per week," he said.
"Why wasn't this done in the summer? If we had all that staff in place, it may well have been the case the system may not have collapsed.
"So why is the recruitment only happening now, and why wasn't all of that additional staff that could have been employed during the summer months, why were they not put in place? We're in the middle of the second wave.
The HSE's Niamh O'Beirne told the committee that over the summer months, staff deployed to contact tracing had come from universities, parts of the HSE, defence forces and public services. However, those staff returned to their roles.
"We began the recruitment process in late August, we had to develop role descriptions and get them approved and put them out," she said.
"They went out over the month of August with a bigger campaign beginning in September.
"We had 2,500 applications go through and interview people, and then go through your standard compliance checking, and that's what's been going on over the last number of weeks and months.
"It's not ideal that we didn't have enough staff as we mentioned before.
"The virus went from 544 cases to 1000 overnight.
"Moving from six weeks ago, 8,500 calls, to 40,000 calls, and we had to meet the demand, but it did exceed the capacity we had at that time."
Ms O'Beirne also told the committee the median for contact tracing to complete is now one day.
Social Democrat co-leader Roisin Shortall pointed out there was a difference between the HSE evidence to the committee and the published statistics on their website which states 3.8 days.
The committee also heard that some contact tracers were being verbally abused on the phone and had been left shaken by the experience.