Over the past year, viewers of the regular Downing Street coronavirus briefings have become accustomed to the different medical and health experts advising the government's response to the Covid pandemic.
The quartet of Chris Whitty, Patrick Vallance, Jenny Harries and Jonathan Van-Tam have become household names as they explain the often complex intricacies around the virus and the global outbreak.
Mr Van-Tam was appointed deputy chief medical officer for England in October 2017 and, following the virus outbreak, joined the government's expert advisory group known as the Vaccine Taskforce.
He has become a consistent presence during the pandemic and is known for his use of metaphors to help explain certain scenarios - but what else do we know about the professor? Let's find out.
Who is Jonathan Van-Tam?
Mr Van-Tam is a specialist in respiratory diseases, such as influenza, and pandemic preparedness - and has offered advice to the government since the Covid outbreak began.
He has spent most of his career in academia and public health since he graduated in medicine from the University of Nottingham in 1987. He was awarded a doctorate of medicine in 2001.
Other qualifications include Fellowships of the Faculty of Public Health, Royal College of Pathologists and the Faculty of Pharmaceutical Medicine.
Born in Boston, Lincolnshire, on 2 February 1964, Mr Van-Tam was educated at the Boston Grammar School before he earned a place at a university he now teaches at.
His grandfather, Nguyen Van Tam, is a former Prime Minister of South Vietnam.
Who is Jonathan Van-Tam's wife?
Jonathan Van-Tam’s wife, Karen, is a former nurse.
The couple live in a small village outside of his hometown of Boston and have three children.
According to an interview with the Independent, Mr Van-Tam says he tries to “turn medicine into stories” and tests out his metaphors on his wife before sharing them in the press briefings to the viewing public.
He soon pricked the interests of viewers when he urged the public not to “tar the pants” out of social distancing guidance and used a train metaphor following the approval of the Pfizer / BioNtech vaccine.
He told viewers: “The train has now slowed down safely. It has now stopped in the station and the doors have opened – that was the authorisation by the MHRA. What we need now is for people to get on that train and travel safely to their destinations.”
Does Jonathan Van-Tam have a Boston United tattoo?
Supporters of Boston United Football Club soon recognised Mr Van-Tam as a Pilgrims fan when he wore a tie in the team’s colours at an early press briefing.
And has since revealed he is considering getting a tattoo once the pandemic has passed when he appeared on ITV’s Good Morning Britain programme.
Mr Van-Tam said in discussion with Piers Morgan: “I'm primed for this. I get up at seven o'clock and see what mood you two are in and see how much of a bashing I'm going to get at eight o'clock.
“Seriously, on tattoos, the subject does come up quite regularly in the Van-Tam household. But it's about whether, when the moment is right, when all this pressure is finished and maybe I'm in a quieter phase of my career, I'll have a little left deltoid BUFC.”
Why has the UK’s vaccine rollout slowed?
In a series of interviews conducted on Wednesday 24 February, prof Van-Tam - sometimes referred to as JVT - was asked why the vaccine rollout had slowed since reaching the 15 million mark.
"That's really very simple to explain. There are always going to be supply fluctuations. These are new vaccines and by and large the manufacturers have never made them or anything like them before," he told Sky News.
"The process of making a vaccine is one where you set the equipment up and leave it all to do its thing - a bit like beer making really - and what you get at the end is not identical every time in terms of the yield.
"You do get batch size variations and that's natural. It's going to take a few months before the manufacturers get into this confident and very steady manufacturing routine.
"On top of that there are global supply constraints. In the UK, we are in an amazing place compared to so many parts of the world. Everyone is looking for vaccines.
"We've been very clever. We've been very much on the front foot in getting access to vaccines. We have secured supplies of many more types and they will come on stream at different time points and rates in 2021.
"Am I confident in the long term that we are going to meet our ambitions through vaccine supply? Yes, I am.
"Do I think this slow down, which is evident in the numbers of the last few days is going to pick up again? Yes, I do."