This theory, posited by several experts, is because they didn’t mix during this time, children weren’t exposed to all the viruses other children would have been exposed to during this time.
As a result, a specific set of children have a lower immunity to common viruses than other children on either side of this cohort.
While under-fives are the main victims of this outbreak, the UK Health Security Agency (UKHSA) has said as part of its investigation “a small number of children over the age of 10 are also being investigated as possible cases”.
Fortunately, while children are becoming ill none have so far died from the outbreak in the UK.