Odds of Influenza in Patients Receiving Intra-articular Corticosteroid Injections: A Cohort Study

Area of Science:

• Rheumatology
• Infectious Disease Epidemiology

Background:

• Intra-articular corticosteroid (IACS) injections, while localized, can lead to systemic absorption and potential immunosuppression.
• Understanding the impact of IACS on susceptibility to common infections like influenza is crucial for patient management.

Purpose of the Study:

• To investigate the association between receiving IACS and the odds of contracting influenza.
• To explore how factors like the timing of IACS, joint size, and vaccination status modify this association.

Main Methods:

• A retrospective cohort study matched 23,368 adult patients who received IACS with an equal number of controls without IACS.
• Primary outcome was the overall odds of influenza; secondary analyses examined specific risk factors.

Main Results:

• No overall difference in influenza odds was observed between IACS recipients and controls.
• However, patients receiving IACS during influenza season had significantly higher odds of influenza (OR, 1.34).
• This increased risk was particularly pronounced in unvaccinated patients receiving IACS during influenza season (OR, 1.41), while vaccinated patients showed no increased risk.

Conclusions:

• IACS injections administered during influenza season are associated with an elevated risk of influenza.
• Influenza vaccination appears to be a protective factor, mitigating the increased risk associated with IACS.
• Patients receiving IACS should be counseled regarding infection risks and the critical importance of influenza vaccination.