The number of people told to shield in England will almost double thanks to a computer model - as the time period for shielding is extended by a month to March 31.
The Government has identified almost two million more people at greater risk from Covid who will be ordered to shield.
The NHS will send letters to patients in the coming weeks and allow them to move up their vaccine priority group.
Advice was to shield until at least February 21 - but it has now been extended for all shielders until March 31, the government announced today.
The two major changes were announced by the Department of Health and Social Care.