As defined by the government, extremely vulnerable people are those with certain condition that put them at higher risk of severe illness from the Covid-19 strain of the cornavirus. This includes people who have had organ transplants, or who have specific cancers or respiratory conditions. Supermarkets are trying to ensure that all their vulnerable customers have access to everything they need via home deliveries.
How do I register as a vulnerable customer?
Supermarkets are working from government lists identifying who the vulnerable people who have online accounts with them are. You can register as a vulnerable person, or on behalf of someone else on the government website