Figure 1. Appropriate location for vaccine administration in the deltoid, using the acromion as a landmark. The base of the triangle is approximately two to three fingers below the acromion (top line) to avoid the shoulder capsule and bursa.

The apex of the triangle lines up with the anterior axilla (bottom line) to form a triangle (yellow) and ideal injection site (green circle) atop the deltoid muscle for injection. The patient pointed to an injection site (red star) that was a subjective two inches below the deltoid muscle.