Avoiding shoulder injury from intramuscular vaccines
Authors: R H Behrens, Vipul Patel
Journal: The Lancet (2021)

With the roll-out of COVID-19 vaccination programmes to tens of millions of people, some individuals might receive vaccines, which have received rigorous safety checks and approval from regulatory bodies, via intramuscular injection. However, the safety around the technique used and the site of injection, in particular, has received little attention. As recommended by the Joint Committee on Vaccination and Immunisation (JCVI), adults aged 16 years or older will be the main population receiving the intramuscular vaccine. The JCVI recommends the deltoid muscle as the optimal injection site, shown graphically as a triangle with the base starting around 1–3 cm below the acromion (appendix).1Public Health EnglandImmunisation procedures: the green book. March 20, 2013. In: Immunisation against infectious disease.https://www.gov.uk/government/publications/immunisation-procedures-the-green-book-chapter-4Date accessed: December 21, 2020Google Scholar However, this site is not universally accepted as the most appropriate; other organisations advocate alternative sites, such as a triangular region with the base around 5 cm below the acromion and the apex at the level of the axilla apex (approximating the middle third of the deltoid muscle),2New Zealand Ministry of HealthVaccine administration.in: Immunisation handbook 2020. Ministry of Health, Wellington2020: 48-60Google Scholar or midway between the acromion and the deltoid tubercle.3Cook IF An evidence-based protocol for the prevention of upper arm injury related to vaccine administration (UAIRVA).Hum Vaccin. 2011; 7: 845-848Crossref PubMed Scopus (36) Google Scholar, 4Nakajima Y Mukai K Takaoka K et al.Establishing a new appropriate intramuscular injection site in the deltoid muscle.Hum Vaccin Immunother. 2017; 13: 2123-2129Crossref PubMed Scopus (28) Google Scholar The site closest to the acromion and origin of the deltoid has several anatomical structures within its vicinity, including the posterior circumflex humeral artery, the anterior branch of the axillary nerve (located 5 cm below the acromion lateral border), and the subacromial–subdeltoid bursa.2New Zealand Ministry of HealthVaccine administration.in: Immunisation handbook 2020. Ministry of Health, Wellington2020: 48-60Google Scholar The subdeltoid bursa can extend to 4·0 cm below the acromion and 1·3 cm below the skin. A range of injuries have been reported to the Vaccine Adverse Event Reporting System database in the USA following vaccination (mostly for influenza). Injuries were predominantly shoulder pain and dysfunction (due to pain, joint-range restriction, bursitis, and stiff shoulder), and patients reported that the vaccines were administered "too high" on the arm.5Hibbs BF Ng CS Museru O et al.Reports of atypical shoulder pain and dysfunction following inactivated influenza vaccine, Vaccine Adverse Event Reporting System (VAERS), 2010–2017.Vaccine. 2020; 38: 1137-1143Crossref PubMed Scopus (36) Google Scholar Spanish pharmacovigilance organisations have similarly reported bursitis and other shoulder injuries following intramuscular vaccination administered in the deltoid. Anthropometric studies of the optimal site of vaccination have identified that the safest anatomical site in adults of both sexes would be approximately (varying by size and sex) 7–13 cm below the mid-acromion, anatomically midway between the acromion and the deltoid tuberosity (appendix). This region avoids the anterior branch of the axillary nerve or the subacromial–subdeltoid bursa.3Cook IF An evidence-based protocol for the prevention of upper arm injury related to vaccine administration (UAIRVA).Hum Vaccin. 2011; 7: 845-848Crossref PubMed Scopus (36) Google Scholar, 4Nakajima Y Mukai K Takaoka K et al.Establishing a new appropriate intramuscular injection site in the deltoid muscle.Hum Vaccin Immunother. 2017; 13: 2123-2129Crossref PubMed Scopus (28) Google Scholar The risk of injury can be further reduced by the recipient placing their hand on the ipsilateral hip (ie, abducting the shoulder to 60°) when receiving the injection. This manoeuvre reduces exposure of the subacromial–subdeltoid bursa to injury. An injection administered at 90° to the skin's surface with a 25 mm needle routinely penetrates at least 5 mm of muscle in men and women. Updating policy and training vaccinators to safely administer the vaccine in the appropriate intramuscular site will be essential for ensuring efficacy of the vaccine, as placement in a bursa or joint will prevent immune system exposure, and for increasing comfort and reducing pain in vaccine recipients. We declare no competing interests. Download .pdf (.17 MB) Help with pdf files Supplementary appendix