The Green Book states that this should include "asthmatics that require continuous or repeated use of systemic steroids or with previous exacerbations requiring hospital admission".
Our searches (v3.0 and below) are including patients prescribed regular inhaled steroids or who have had a hospital admission in the last 5 years. The EMIS in-house searches work in a similar way.
We have done this as the flu at-risk patient cohort includes asthmatics taking inhaled steroids and because it is impossible to search for only patients taking high-dose inhaled steroids (that have a systemic effect).
We are considering whether we should review these searches and only include those asthmatics taking regular oral steroids. This would significantly reduce the cohort size but it may mean that some at-risk patients are missed. We are taking advice on this and will update you here if we revise this search.