Sudden shoulder swelling in an elderly man after the flu shot

This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and nomodifications or adaptations aremade. © 2020 The Authors. JACEPOpen published byWiley Periodicals LLC on behalf of the American College of Emergency Physicians. muscle thought to be a result of vaccine administration. Consequently, the fluid collection was drained by orthopedics at bedside and the fluid sent for culture showed no bacterial growth. The patient was ultimately dischargedwith routine outpatient follow-up. The influenza vaccine likely triggered an acute inflammatory arthritis because of the temporal and anatomical relationship of vaccine administration and localized joint swelling. Vaccines contain adjuvant stimuli that have been proposed to cause a spectrum of immune-mediated phenomena called Autoimmune/inflammatory Syndrome Induced by Adjuvants (ASIA).1 The aluminum component of the influenza vaccine may have led to the development of adjuvantinduced autoimmunity responsible for the various post-vaccination sequelae seen clinically. Furthermore, vaccine injection creates a depot of antigens that are released slowly, creating a sustained stimulation of the immune system, activating the inflammatory cascade and exacerbating the swelling.2 Influenzavaccination is anessential preventivemeasure in the interest of public health, yet it is important to recognize and consider the potential harm to the individual and weigh that risk against the public health benefit.