First Covid vaccination administered in Northern Ireland
The first person to receive the vaccine in Northern Ireland was a 28-year-old nurse from Dundrum in Co Down.
Joanna Sloan is sister in charge of Covid vaccination for the Belfast Health and Social Care Trust, Northern Ireland's largest.
She received the Pfizer/BioNTech dose on Tuesday morning at a mass vaccination centre at the Royal Victoria Hospital.
Ms Sloan, who is just one of an 800-plus team of vaccinators that will be involved in the subsequent rollout programme, said it felt like a "huge moment" in the battle against the pandemic.
Northern Ireland's chief medical officer, Dr Michael McBride, said today is a remarkable one.
"We can begin to look to the future with a degree of optimism, with this vaccine and other vaccines and more effective treatments," he said.
"Hopefully in the future Covid-19 will become a more manageable disease and we will begin the pathway to a more normal life."
He added that he did not think this day would come so soon, 10 months after Covid-19 was discovered, as opposed to the more normal 10 years taken to develop vaccines.
He recalled the sacrifices and harm caused by the virus as well as the number of lives lost, and warned there will be more challenging months ahead.
Reacting to the news, deputy First Minister Michelle O'Neill has described Tuesday as a "big day".
She said: "Joanna is certainly leading the way.
"It shows that there is some confidence and optimism about next year and what that will bring, the return to some normality for all of us.
"I am delighted that today is the first step forward and it will be received very positively by the public."
Watch: Reaction from Stormont:
Meanwhile, Stormont Health Minister Robin Swann also described it as a "hugely important day" but cautioned the full programme will take months to deliver.
Healthcare workers across the region will be able to get the vaccine through the remainder of December at seven centres spread across the region.
On Monday, Mr Swann announced care home residents will also be prioritised in the first phase.
He said deployment of the vaccine to care homes will proceed in the coming days.
The minister said officials have been working on the logistical requirements for the Pfizer/BioNTech vaccine and reached a solution involving mobile teams operating from the different trust vaccination centres.
"We are currently considering how these arrangements might be extended to include over-80s in the community," Mr Swann added.
Stocks of coronavirus vaccine arrived in Northern Ireland on Friday.
There are 25,000 doses in the initial batch of the vaccine.
The stocks have been taken to a central storage facility operated by a private company. The location is not being disclosed.
Two of the facilities are located on hospital grounds - at the Ulster Hospital in Dundonald and Belfast's Royal Victoria Hospital - and the rest in leisure centres.
The centres will operate 12 hours a day and seven days a week.