In the UK there are 1.2million NHS workers in England alone you then need to factor in Scotland, NI and Wales., if you then consider any other persons such as NHS volunteers 700,000 of them or other public facing key workers involved in the fight like police, military, Border Force, council employees, Public Health bodies etc etc Then there are charity workers exposing themselves to help people in unfortunate circumstances.
Thats the tip of the iceberg and a lot of people to consider. The criteria would have to be very strict to make such a medal feasible i.e. front line carers exposing themselves to high risk of infection. But then that would denigrate other essential persons who have placed themselves at high risk of infection for example cleaning staff, in hospitals. We need to see how this pans out in the long term, as it is just the beginning.
You may be right that like WW2 a series of medals needs to be considered dependent on role. Call me a cynic but the one factor in the UK that will without a doubt influence any such decisions will be the role the military play in this. If they are deployed in significant numbers, then standby for medals to be issued. If not then other than recognising the acts of a few key individuals such as the usual bigwigs at the top, or those that have sadly paid the ultimate sacrifice or placed themselves at immense risk is the more likely option.