Cancer operations have been cancelled and exhausted off-duty staff called in to work after the current Covid-19 wave hit two weeks earlier than expected.
Health officials have said a combination of staff shortages, a failure to reach the 85% vaccination target and the new surge has contributed to the latest crisis.
It comes after concerns were raised over information provided to the Executive to help it make life-or-death decisions about pandemic restrictions.
Chief scientific adviser Professor Ian Young appeared in front of the Stormont health committee yesterday and was pressed for answers about interruptions to services as the NHS struggles to cope with the influx of Covid patients.
Colm Gildernew, chair of the committee, revealed harrowing details of a constituent who was contacted the day before her red flag cancer operation and told it had been cancelled.
The Sinn Fein MLA said the woman has no idea when the operation will happen and she is now isolating indefinitely so she is free from Covid when a theatre slot becomes available, meaning her children are unable to return home.
He asked: “What has gone wrong on this occasion that sees us back in this situation that we have been in in previous surges, and how could that have been avoided?”
Prof Young said the current wave had occurred when “exhausted staff” have leave booked, while a significant number of staff are self-isolating due to larger case numbers, and cases have “larger numbers of contacts as a result of Executive relaxations”, which have seen “society moving back to normal”.
Paul Cavanagh from the Health & Social Care Board said while hardworking staff have been doing their utmost to ensure continuation of services, the system has reached “tipping point”.
He said a call was put out at the weekend asking off-duty staff to come into work as the current wave happened “two weeks before we expected”.
Mr Gildernew asked for reassurance the Executive had been provided with information about potential pressures on the NHS ahead of crucial decisions over the relaxation of restrictions.
Prof Young said while modelling does not include projections relating to impact on service delivery, the Executive does receive “an update in terms of the broader picture around the pressure which are faced by the healthcare system”.
Earlier in the evidence session Prof Young said there has been a drop in cases and explained there are two potential reasons for this.
He said the recent hot weather could be the driving force. He warned case numbers are likely to rise again.
Alternatively, he said it could be because younger people are the main driving force for the current surge and a large proportion are becoming immune. This would result in case numbers continuing to drop.
However, he explained it will be next week before the trajectory of the pandemic becomes clear.
Prof Young also described the devastating impact of the failure to reach vaccination targets and revealed Northern Ireland lags behind the rest of the UK in relation to uptake.
He said: “We modelled 85% by the end of the month, which we felt was achievable, and actually we also modelled 90% at the end of the month, which is the position that has been reached in England, Scotland and Wales.
"If we could have achieved 90% by the end of the month we would have reduced the size of this peak by one half and we would have reduced our hospital pressures by one half. It would have made an absolutely enormous difference.
"As it happens, we, during the middle of the month, decided that it looked as if, for multiple reasons, and this is not straightforward, something about Northern Ireland… not lack of effort or in terms of messaging, but for some reason our population is more reluctant to come forward for vaccination than the population in other parts of the UK.”
The committee also heard from Patricia Donnelly, who heads up the vaccination programme. She revealed rules stopping people from taking photographs inside mass vaccination centres were axed in a bid to increase the uptake of the jab in young people.
Officials decided to allow people attending for their jab to take selfies in the hope young people would post the pictures on social media and encourage friends to come forward for vaccination.
It is one of a range of measures put in place after the uptake rate of the vaccine "went off a cliff" after the programme opened up to younger people.
Ms Donnelly explained: "We were the first in the UK to open to the under 30s and that's been open for two months. However, their uptake has been incredibly slow.
"We are comparable, and indeed ahead, of other parts of the UK and Ireland until we get to the under 50s. From 40 to 49, (it’s) only 83% of the population, and then it drops down further to 70% of 30 to 39. They're still coming forward, but slowly, and we've not yet reached 60%."
Yesterday 1,471 new positive cases were recorded, and a further two deaths.