The decision to change the tiers comes after officials consider several interacting factors.
A Department for Health and Social Care spokesman said: “Tiering decisions are based on a range of factors including how quickly case rates are going up or down, cases in the over 60s, pressure on the NHS and local circumstances.
“Decisions are made by ministers, informed by leading epidemiologists, public health experts, and clinicians.”
Using these criteria, the Government could choose to move several areas up or down the tier system.
