Odds of Influenza in Patients Receiving Intra-articular Corticosteroid Injections

Objective: Although intra-articular corticosteroid (IACS) is injected locally, some systemic absorption occurs, potentially causing immunosuppression in recipients. This study examined the odds of influenza in patients who received IACS compared with matched controls.Design: Adults in the authors' health system who received IACS from May 2012 through April 2018 were 1:1 matched to adults without IACS. The primary outcome was overall odds of influenza. Secondary analyses examined influenza odds by timing of IACS, joint size, and vaccination status.Results: A total of 23,368 adults (mean age, 63.5 yrs, 62.5% female) received IACS and were matched to a control. Although there was no difference in influenza odds by IACS status overall (odds ratio, 1.13; 95% confidence interval, 0.97-1.32), patients receiving IACS during influenza season had higher odds of influenza than matched controls (odds ratio, 1.34; 95% confidence interval, 1.03-1.74). Furthermore, unvaccinated patients who received IACS during influenza season had higher influenza odds compared with matched controls (odds ratio, 1.41; 95% confidence interval, 1.04-1.91]), whereas there was no difference among vaccinated patients.Conclusion: Patients receiving IACS injections during influenza season had higher odds of influenza. However, vaccination seemed to mitigate this risk. Patients receiving IACS injections should be counseled on infection risk and importance of vaccinations. Further research is needed to examine IACS effects on other viral illnesses.