On March 21st the government issued new guidance on shielding and protecting people defined on medical grounds as extremely vulnerable from COVID-19.
Shielding is a measure to protect people who are clinically extremely vulnerable by minimising all interaction between those who are extremely vulnerable and others.
The full government guidance is published here. It explains what measures are being taken by the NHS centrally , hospital trusts and GP surgeries to notify people who are considered to be in that group.
The latest up to date guidance from NHS England for all other people can be viewed on the following link.