A retrospective cohort study found that shoulder injury occurred in fewer than 1 in 10,000 patients who received an intramuscular vaccinations administered in the deltoid muscle between April 2016 and December 2017 (pre-COVID-19 pandemic). The authors say that given the high burden of shoulder conditions, clinicians should pay attention to any factors that may further increase risks. While shoulder conditions may be preventable if caused by inappropriate vaccine administration, their study did not determine the cause of vaccine-associated shoulder injuries. The findings are published in Annals of Internal Medicine.