It's worth separating the two types of 'high risk': There's 'high risk of having a severe response to COVID' and 'high risk of getting COVID'. The former (e.g. elderly) are not always the same as the latter (healthcare workers) - but there are some overlaps (e.g. care homes).

My hunch is most of the queues for vaccines will be type A e.g. the elderly. Not necessarily more likely to have COVID, but more likely to be at risk of severe symptoms if they were to get it.