They included people who have received organ transplants or are on immunosuppression drugs.
Faye Law, senior adviser and conciliator at the Advisory, Conciliation and Arbitration Service (Acas) says these people, and millions of others considered extremely vulnerable, are not expected to return to their workplace.
Wherever possible they should work from home or be furloughed under the government scheme which currently pays 80% of an employee’s salary up to £2,500 a month.
Separately, people who are at-risk – but did not receive a letter from the government encouraging them to shield for 12 weeks – could have to return to work, but Ms Law says their employer should ensure strict social distancing rules are in place.
But employment law expert Simon Rice-Birchall, from Eversheds Sutherland, thinks it would be difficult for an employer to force people to return to an office if they have shown that they can do their job from home.
Those who are told to go in will not be entitled to sick pay if they choose to stay at home because they are worried about contracting the virus, he says.
“Somebody that’s vulnerable at home isn’t sick,” he says.
Can my boss make me work during lockdown?
At the moment, government advice to work from home effectively overrides the content of most employment contracts, which require us to go to work, says Mr Rice-Birchall.
But David D’Souza from the Chartered Institute of Personnel and Development says his organisation has been told about employers forcing people to work.
“That is of huge concern in terms of people’s physical and mental wellbeing,” he says.
“And whilst it’s understandable that organisations are trying to sustain themselves, doing that by having people working under conditions of duress is not what you would want to see in a modern economy.
“Any return to work should only be done if these criteria can be met: It’s necessary, it’s safe, and it’s mutually agreed”.
Tim Sharp, from the Trades Union Congress, says forcing people to return to work like that could put employers on the wrong side of the law.
For example, you’re not required to work if you hold “a reasonable belief that there’s a serious and imminent threat” to your health, he says.
He thinks that would apply where an employer is not following public health guidelines.
“If [after discussing with employer] you remain concerned that your employer is not taking all practical steps to promote social distancing then you can report this to your local authority or the Health and Safety Executive who can take a range of action, including where appropriate requiring your employer to take additional steps,” the government advises.
Which workers are likely to return to work first?
The Prime Minister encouraging construction workers and those on factory lines back to work was expected, in part because those roles are simply impossible to do remotely.
Workers in those sectors will likely to return to work in the coming days and weeks, according to Charlie Netherton, from Marsh Risk Consulting.
At the other end of the spectrum, professional services firms have proved they can operate quite effectively with the majority working from home.
As a result, Mr Netherton says the government is not likely to prioritise getting office workers back to their desks.
But the picture becomes complicated in the entertainment and retail sectors, because it is unclear when people will feel comfortable returning to shops, bars and restaurants.
“I suspect a number of people will be cautious,” Mr Netherton says questioning whether it would be economically viable for restaurants to open their doors again, even if they were allowed to do so.
“Retail organisations are keen to start selling again, the challenge they have is understanding when the customers will return,” says Mr D’Souza from the CIPD.
I’m currently furloughed so cannot return to work, how will I be affected?
Coronavirus restrictions mean the work of many firms has come to a standstill. Pubs, restaurants, cafes, travel firms and estate agents are among those hit.
The Government says about 800,000 employers have reported furloughing workers since 20 April, when the programme started.
Some firms have forced staff to choose between working for 80% of their salary or being furloughed.
Companies don’t have to keep on any employees when furlough ends, and cannot use these payments to subsidise redundancy packages.
The hope is that by the time the scheme ends, restrictions will have lifted and businesses can start paying full salaries again.
But employers could face allegations of discrimination if they only keep on staff who worked through the crisis, according to Ms Law.
“You could find it indirectly discriminates on the basis of disability, because people might be more likely to choose furlough as an option because they’ve got an underlying health condition,” she says.
“Or it might also be sex discrimination because it’s more likely the case that it’s the woman in a household that stays at home with the children.”