Chief Medical Officer Dr Michael McBride has said the north faces the most serious moment of the pandemic to date.
He described a very difficult time for the health service and urged the public to follow the "stay at home" message.
Dr McBride said recent high case numbers will translate to admissions into hospital, intensive care and deaths.
"As we roll out this vaccine we are making very significant progress, it is not time now to relax, it is not now time to lose our grip, it's now time to redouble our efforts and keep on top of this virus until such times as we can protect those most vulnerable by getting them vaccinated," he said.
Chief scientific adviser Professor Ian Young said the R-number for cases of coronavirus was somewhere between 1.5-1.9 last week, but since then has "passed the peak" and the R-number has "fallen to significantly lower levels in terms of cases".
"We still have a long way to go," he warned, pointing out that hospital admission rates continue to rise due to the time lag between high case numbers and hospital admissions.
"We expect that to continue for a little longer and pressures in hospitals will not peak until some time in the last weeks in January.
"What we do now is critical to determining how rapidly those numbers fall once they peak, and that's the challenge.
"We can see that the current restrictions work in terms of falling case numbers, we need to make sure that that benefit, that the effort is sustained so that hospital admissions, inpatient numbers, ICU occupancy and deaths will also fall as quickly and steeply as possible towards the end of this month."
Prof Young said the fall in case numbers shows that staying at home works, adding "it must be sustained".
Patricia Donnelly, head of the Covid-19 vaccine programme in Northern Ireland, said almost 100,000 jabs have so far been administered since it started on December 8.
She said a "very flexible agile" programme has been produced.
Phase one, involving older adults in care homes and care home workers, is 92% complete, with the remaining outstanding due to Covid outbreaks.
Ms Donnelly described a "very high" level of uptake for the most vulnerable group.
The over-80s group is currently being worked through via GP surgeries, as well as the health staff group.
"We are coming to the end of our phase one... and I'm happy to report that we are approaching 100,000 vaccines administered, of these 86,000 will have been first vaccinations through trusts and GPs," she said.
"We are about to enter phase two, which is for the over 75-year-olds."
Patricia Donnelly said there are seven large vaccination sites across Northern Ireland that will operate seven days a week from 8am to 8pm as well as a large number of mobile teams. Chief medical officer Dr Michael McBride praised a "firm, very solid" start to the vaccination programme.
Speaking to The Irish News yesterday, Health Minister Robin Swann discussed the possibilty of vaccination hours being increased.
He said: "We've been running our seven regional centres since December and as we get access to more vaccines we will increase our hours. It’s a piece of work we’re already looking at. Will we go 24hrs? I’m not sure. The thought of going out at 2am or 3am may be attractive to some but whether it’s actually practicable on a full-scale operation at the time of the morning is another thing."
First Minister Arlene Foster has praised the reduction of the R-number in Northern Ireland from 1.8 to around 1.1.
Speaking at a joint press conference with Deputy First Minister Michelle O'Neill in Dungannon, Mrs Foster urged the public to "take personal responsibility and do the right thing".
She urged "simple and everyday choices" such as phoning family and friends rather than visiting, doing one big food shop rather than nipping out each day and not going into the workplace when people don't have to.
"I do appreciate the costs these restrictions are having, I appreciate the weariness, we're all sick and tired of restrictions but we absolutely must do it to get through it," she said.
"There is light at the end of the tunnel, the vaccine is rolling out at a very good rate, we can see a route back to normality but it will take us months to get there."
Mrs Foster expressed disappointment that some employers and business owners are requiring their staff to attend work when people can work from home, while some businesses should not be open at all.
"That's quite a selfish spirit I have to say, and it's not going to help us to beat the virus and keep people safe," she said.
"And for those who say but someone else is doing it, as my mother used to say, if they put their hand in the fire, there is no need for you to follow it."
Mrs Foster said she, along with Deputy First Minister Michelle O'Neill, will be speaking to the PSNI chief constable later around compliance.
Deputy First Minister Michelle O'Neill stressed the "immense pressure" that the health service is under.
"It's something we all have an ability to do something about," she said.
She said 1,205 new positive cases of the virus were notified, with 751 people with Covid in hospitals and 55 in intensive care.
"This number is only going to rise, we're in for a very tough number of weeks ahead, the pressure will mount on the health system and we all need to adhere to the public health advice," she said.
Michelle O'Neill also expressed concern at employers asking staff to come into work and retailers not operating in line with the spirit of the restrictions.
"That's not only unfair to the smaller retailers who are complying with the requirement to remain closed but it also goes against all the effort to stop the spread of coronavirus right across the community," she said.
"We have agreed to convene an urgent roundtable meeting with the retail sector, including the larger retailers, supermarkets, supply chains, along with the councils and the head of the Health and Safety Executive.
"That will give us an opportunity to address the issues which we have identified as problems and give us the opportunity to reinforce that message again of the need to comply with the spirit and the letter of the restrictions."
Michelle O'Neill added: "Today the message from us is one of reinforcement, it is to say again people need to stay home, to not leave your home unless it is absolutely necessary and it is for one of the reasons that has been identified.
"Staying at home is the law and no one should leave their home, and we are asking employers to be responsible and only bring their staff in where it is essential.
"We're in for difficult days ahead, the vaccine programme is rolling out... but it's going to take us some months before we get to the point where we have significant vaccinations right across society to make the difference that we all really look forward to."
