The systemic immunosuppressive effects of peripheral corticosteroid injections: A narrative review of the evidence in the context of COVID-19.

introductionInjected glucocorticoid's (corticosteroids) are commonly used in musculoskeletal practice. The current global COVID-19 pandemic has increased attention on the potential for locally injected corticosteroids to exert a systemic immunosuppressive effect and the implications this may have in relation to COVID-19 infection and vaccination.

aimThis narrative review summarises the evidence regarding the potential systemic immunosuppressive effects of peripheral corticosteroid injections in relation to the ongoing COVID-19 pandemic.

methodA narrative review was selected to allow inclusion of evidence related to a diverse range of topics relevant to this subject in order to provide the most comprehensive and clinically relevant guidance for clinicians. RESULTS/DISCUSSION: Current evidence demonstrates that cytotoxic, phagocytic and antigen presenting cells involved in both the innate and adaptive immune responses are suppressed for 48 h post-injection and messenger cytokines that are integral to immune function are suppressed for over 96 h post-injection. This potentially reduces an individual's ability to prevent viral infection, limit early viral replication, and delays activation of adaptive immune mechanisms (T and B lymphocytes) and subsequent viral clearance and elimination. The hypothalamic-pituitary-adrenal (HPA) axis can be suppressed for 2-4 weeks or longer following peripheral corticosteroid injections. The role of the HPA axis in immune function is not fully understood, however this could potentially indicate longer lasting immunosuppression.

conclusionsThis review found evidence of suppression of immune cell numbers for the first 48 h post-injection, cytokines for over 96 h post-injection and HPA axis suppression lasting for 2-4 weeks or longer. There is currently no evidence that these physiological changes translate into a clinically meaningful increased risk of COVID-19 infection or related morbidity or mortality, but there is also no persuasive evidence that they do not. This review discusses the implications of the current evidence in relation to shared decision making, informed consent, risk management and COVID-19 vaccination to provide clinicians with a pragmatic guide to help navigate the current uncertainty regarding the potential immunosuppressive effects of peripheral corticosteroid injections.