This is allowed only when necessary.
Redemptionis Sacramentum (RS) explains, “Indeed, the extraordinary minister of Holy Communion may administer Communion only when the Priest and Deacon are lacking,
when the Priest is prevented by weakness or advanced age or some other genuine reason, or when the number of faithful coming to Communion is so great that the very celebration of Mass would be unduly prolonged” (RS 158; emphasis added).
Also, “Only out of true necessity is there to be recourse to the assistance of extraordinary ministers in the celebration of the Liturgy. Such recourse is not intended for the sake of a fuller participation of the laity but rather, by its very nature, is supplementary and provisional” (RS 151).
In the absence of true necessity, this practice is expressly prohibited. “The practice of those Priests is reprobated who, even though present at the celebration, abstain from distributing Communion and hand this function over to laypersons” (RS 157).
