Matt Hancock said that a communication will be sent to those classed as at risk, which includes people over 70, people with heart, lung and kidney conditions and people who are pregnant.
People with: chronic liver disease, such as hepatitis; chronic neurological conditions such as Parkinson’s disease, motor neurone disease and multiple sclerosis (MS); a learning disability; cerebral palsy and people with diabetes are also classed as vulnerable.
The Health Secretary told Sky News: "The first thing we're going to do is set out exactly what conditions that applies to. We expect about 1.4 million people to then get a communication from the NHS to say that they are part of this and what they need to do.
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"Many of these people have pre-existing health conditions and so will be very worried right now, and I understand that, and they'll need very specific sets of action - for instance, how do you go about still getting your chemo if you have cancer whilst also social-distancing?
"If you have cancer it's particularly important to stay away from other people, but you also of course have got to keep going with your chemotherapy."
He added: "These are some of the most difficult and challenging cases so we'll be getting in contact with them, but if people think that they are on this list and don't receive a communication from the NHS, then they also need to get in contact.
"So that is under way, the money was announced for it yesterday. A combination of money to the NHS and money to councils because they've got a very big part to play in keeping people safe."
A full list of the people who are considered vulnerable to COVID-19 can he found here.
As of Thursday, February 19, there had been 40 confirmed cases of coronavirus in Sheffield and one death. Across the UK, 3,269 people had tested positive and 144 people had died.