Does receiving the influenza vaccine or COVID‑19 vaccine increase the risk of a flare in a patient with Behçet’s disease who is on azathioprine 150 mg daily?

Vaccination in Behçet's Disease Does Not Increase Flare Risk

Both influenza and COVID-19 vaccines can be safely administered to patients with Behçet's disease on azathioprine 150 mg daily, as the vast majority of evidence shows no increased rate of disease flares after vaccination in patients with rheumatic and musculoskeletal diseases. 1

Evidence Supporting Vaccination Safety

The 2022 American College of Rheumatology guidelines explicitly state that non-live attenuated vaccinations (including influenza and COVID-19 vaccines) should be given regardless of disease activity in patients with rheumatic diseases 1. This recommendation is based on extensive evidence showing that:

• The vast majority of studies failed to demonstrate any increased rate of flare after influenza vaccination in patients with rheumatic and musculoskeletal diseases
• Similar results were observed for other vaccinations, though the quality of evidence was lower
• Disease activity does not significantly impact vaccine immunogenicity in most cases

Azathioprine Considerations

Your patient on azathioprine 150 mg daily (which is within the low-level immunosuppression threshold of ≤3 mg/kg/day for most adults) can receive both vaccines without medication adjustments 1. The ACR COVID-19 vaccination guidance specifically states that azathioprine requires no modifications around the time of vaccination 2.

This contrasts with other immunosuppressants like methotrexate or JAK inhibitors, which require temporary holds to optimize vaccine response.

Vaccine Response Considerations

While patients on immunosuppressive medications may have a reduced antibody response to COVID-19 vaccines 3, this does not translate to increased flare risk. The study of Behçet's patients specifically found that those on immunosuppressive medication had lower antibody responses but did not report increased disease flares 3.

Addressing Patient Concerns

Strong concerns exist among patients about vaccines causing disease flares 1, making shared decision-making particularly important. However, you can reassure your patient with the following evidence-based points:

• Multiple large studies in rheumatic disease patients show no increased flare rates
• The theoretical risk of immune stimulation triggering flares is not supported by clinical data
• The benefits of preventing influenza and COVID-19 (which themselves can trigger flares and cause serious complications in immunosuppressed patients) far outweigh any theoretical risks

Rare Case Reports vs. Population Data

While isolated case reports exist (such as one case of frosted branch angiitis post-COVID vaccination in a Behçet's patient 4), these represent extremely rare events that cannot establish causation. Population-level data consistently shows safety.

Practical Recommendations

• Administer both influenza and COVID-19 vaccines without delay
• Continue azathioprine without interruption
• Monitor for typical post-vaccination symptoms (injection site pain, fatigue, myalgia), which are common but self-limited
• Distinguish between expected vaccine side effects and true disease flares
• Schedule routine follow-up rather than special monitoring, as flare risk is not elevated

The evidence strongly supports vaccination in your patient, with no need to hold azathioprine or delay vaccination due to flare concerns.

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