How is it possible that it requires a specific vocation to be a member of a prelature?

Naturally this vocational requirement is not essential to personal prelatures, which could be based on very diverse circumstances, usually linked to social bonds among its faithful.

Naturally this vocational requirement is not essential to personal prelatures, which could be based on very diverse circumstances, usually linked to social bonds among its faithful.

Nevertheless, a vocation could be required if the ecclesial reality itself entailed a specific vocation, which is true in the case of Opus Dei. The Church recognizes and fosters a reality that comes from the Holy Spirit, without whose help the whole prelature of Opus Dei would cease to exist.