An email sent to some staff within the South Eastern Trust appears to give them the chance to register family for early access to a Covid-19 vaccine.
The email said that over-65s, who were known to staff, could book in before the official announcement.
The South Eastern Trust said it would have "lost hundreds of precious vaccine slots" had it not taken the action.
First Minister Arlene Foster has said she would "much rather see people vaccinated than waste the vaccine".
On Tuesday night, the department said those aged 65-69 could register for the vaccine later this week.
BBC News NI has seen a screenshot of the email, so cannot verify when it was sent, nor how many staff received it.
"We have been asked to send this to staff in advance of the regional announcement later this week," the email said.
"Anyone with relatives/friends in the 65 to 69 year age group will be invited to make an appointment to receive the Pfizer vaccine at one of the trust facilities."
The email then lists details of when the vaccine centre is open, as well as details on how to book the vaccine - including a phone number for the booking line.
"Grateful if you could pass this on to anyone you know in that age group.
"More details will be in the media this week but we are keen to get the Thursday/Friday slots filled asap."
BBC News NI understands the announcement that over 65s would be able to register for the vaccine was intended to be made later this week, but on Tuesday evening the department confirmed the rollout had been accelerated.
'Trying not to waste any doses'
BBC News NI has also seen different versions of the e-mail being circulated widely in WhatsApp groups.
The South Eastern Trust confirmed that the e-mail was genuine and that the trust was trying not to waste any doses of the vaccine.
In a statement the trust confirmed: "In advance of the online public booking system going live, we have now commenced a local trawl inviting those aged 65-69 whom we could book manually to fill the early morning slots on the first day.
"We are clear that if we had not done this we would lose hundreds of precious vaccine slots on Thursday morning."
The trust said it was committed to implementing the guidance in relation to the rollout and was "working hard to maximise every vaccine slot".
"The healthcare system in Northern Ireland is under incredible pressure," it said.
"It is vital that the vaccination programme moves forward swiftly and efficiently and that not a single dose of vaccine is wasted."
'Better used than wasted'
Speaking to Good Morning Ulster, First Minister Arlene Foster agreed with the Trust's decision, adding that "no one will be jumping the queue".
"We do not want to risk losing this vaccine. I think wasting the vaccine would be absolutely the wrong message to send to people."
On Tuesday, a decision to allow NI back office health workers to be vaccinated early was criticised by the deputy chair of the government's advisory body.
When asked about the email that the South Eastern Trust sent, Dr Alan Stout, a GP in Belfast said: "They're maybe jumping the gun a little bit on the whole thing."
Dr Stout said he suspected this was due to "the pressure of using up the vaccine" as the Pfizer vaccine "needs to be used once it's been defrosted".
"There's a real pressure on them to use that quickly - our hope is that they use that more for the second doses for the front-line health care workers.
"Certainly there should be no perception of people jumping the queue or people getting priority.
"There's lots of vaccine coming in so nobody is ever going to be left behind with this."
The Department of Health has also confirmed that the Health Minister Robin Swann and chief medical officer Dr Michael McBride have not yet received the vaccine and both will wait until their age group is called.
Scam vaccine warning
Meanwhile, a Londonderry GP has warned against scam callers offering vaccination slots for money.
Speaking to BBC Radio Foyle, Dr Noel Boyle said: "If anyone is ringing and giving you an appointment for a vaccine, no bank details should ever be asked.
"Nothing like that should be asked, if they do it is a fake scam call.
"If a hospital or a practice rings you they will only be asking purely your details to say that you're getting booked - there should be no question of payments."
Both GP practices and regional vaccination centres will be used to vaccinate members of the public from prioritised groups.
People aged between 65 and 69 in NI are to be vaccinated at their local vaccination centre and GPs will vaccinate the over 70s in surgeries at the same time.
Dr Boyle reiterated that people should not ring GP practices. If they are in the correct age bracket they will be contacted by their practice.