Spinal region corticosteroid injections are not associated with increased risk for influenza

Abstract

BACKGROUND CONTEXTSpinal region corticosteroid injections (CSI) are intended to act locally to relieve radicular or axial back pain, however some systemic absorption occurs, potentially placing recipients at risk for immunosuppressive effects of corticosteroids. No previous studies examine whether patients undergoing spinal region CSI are at increased risk for viral infections, particularly influenza—a common viral illness with potentially serious consequences, especially for patients with multimorbidity. PURPOSETo examine odds of influenza in patients who received spinal region CSI compared to matched controls. STUDY DESIGNRetrospective cohort study. PATIENT SAMPLEAdults (n=9,196) who received a spinal CSI (epidural, facet, sacroiliac, paravertebral block) during influenza seasons occurring from 2000 to 2020 were 1:1 matched to controls without spinal CSI. OUTCOME MEASURESThe primary outcome was odds of influenza diagnosis in spinal CSI patients compared to matched controls. Predetermined subgroup analyses examined odds of influenza diagnosis based on vaccination status and injection location. METHODSAn institutional database was queried to identify patients that received spinal CSI during influenza season (September 1 to April 30) from 2000 to 2020. Patients were matched by age, sex, and influenza vaccination status to controls without spinal CSI within the specified influenza season. Influenza diagnosis was ascertained using International Classification of Disease codes and data was analyzed using multiple logistic regression adjusted for comorbidities associated with increased risk for influenza. RESULTSA total of 9,196 adults (mean age 60.8 years, 60.4% female) received a spinal CSI and were matched to a control. There were no increased odds of influenza for spinal CSI patients as compared to matched controls (OR 1.13, [95% CI, 0.86–1.48]). When subgroups were examined, there were also no increased odds of influenza for spinal CSI patients based on immunization status (unvaccinated or vaccinated) or spinal injection location (epidural or non-epidural). CONCLUSIONSSpinal region CSI was not associated with increased odds of influenza or reduced vaccine efficacy. This is reassuring given the analgesic and functional restoration benefits of these injections. Assessing risk of viral infection associated with spinal CSI is particularly relevant in the era of the COVID-19 pandemic, and further work is needed to address this issue.