Dr Gabriel Scally says the start of the coronavirus vaccine programme in the UK is a 'great day'.
The public health expert is 'particularly pleased' that a Fermanagh woman was the first person in the western world to receive an approved vaccine.
Enniskillen native Margaret Keenan became the first member of the public to be vaccinated outside of a clinical trial this morning.
The 90-year-old has lived in Coventry for the past 60 years, and she received the Pfizer jab at University Hospital Coventry.
Across the UK, officials administering the vaccine are the first people getting it, before it's fully rolled out to residents in care homes, healthcare workers and the elderly.
Dr Scally - public health physician, former director of Public Health for Belfast and Professor of Public Health at University of Bristol - told The Hard Shoulder it's a big day.
He said:"Full credit to everyone across the world who has worked on it - over 200 candidate vaccines, and several of them now either approved or waiting approval. It's a great effort.
"I'm so pleased, but we've a winter to get over us. We've got to get the vaccine rolled out to as many as possible."
Dr Scally suggested the vaccination programme shows what the British government can do when they use the National Health Service (NHS) and the Health & Social services in Northern Ireland.
He said he's very impressed by the swift rollout, especially considering how cold the vaccine has to be kept for a two or day before it's injected.
Margaret Keenan, 90, is the first patient in the United Kingdom to receive the Pfizer/BioNtech covid-19 vaccine at University Hospital, Coventry, administered by nurse May Parsons, at the start of the largest ever immunisation programme in the UK's history. Picture by: Jacob King/PA Wire/PA ImagesHe explained: "It's great a Fermanagh woman got it first in the world... an approved vaccine. I'm very pleased about that in particular.
"I spent so many years in Belfast trying to persuade people to get their children immunised. The vaccines were absolutely brilliant, and they were [for] diseases nobody would never hear of now.
"Unfortunately, one or two - like measles - have made a comeback... there were awful claims made about the MMR [vaccine]. Some parents hesitated, and I'm afraid a lot of children paid the price."
He said everyone who can should have the coronavirus vaccine when it's available, as even a 90% efficacy would mean a significant number of people would not be protected even after receiving the jab.
He said 90% is 'great for a vaccine', but mass immunisation is the way to really get the virus rates reduced.
