Upper arm injury related to vaccine administration (UAIRVA) is an infrequent but increasingly recognised complication of deltoid muscle vaccination. Vaccine administration reported injury to the subdeltoid/subacromial bursa, anterior branch of the axillary nerve and the radial nerve presumably reflects the lack of awareness of the anatomical position of these structures in and near this muscle and the multiplicity of methods for the selection of the injection site in the muscle. An evidence based protocol for safe vaccine administration into the deltoid muscle is presented. This was developed using anthropometric measurements of the surface anatomical landmarks in adults who regularly receive intramuscular injection of vaccines into the deltoid muscle (adults ≥ 65 years old) and mapping the position of structures potentially injured by injection observed in ultrasonographic and cadaveric studies. The mid point of the muscle (midway between the acromion and the deltoid tuberosity) with the arm abducted to 60° is a safe site for injection. The protocol for vaccine administration in this way involves the vaccinee placing the hand on the ipsilateral hip with the vaccinator then placing their index finger on the acromion and their thumb on the deltoid tuberosity and administering the vaccine at midpoint between these anatomical landmarks.