What is the increased risk of COVID-19 infection for an otherwise healthy patient with Behçet’s disease taking azathioprine (Imuran) 150 mg daily who is unvaccinated?

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Last updated: October 2, 2026 • View editorial policy

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Risk of COVID-19 in Unvaccinated Behçet's Patients on Azathioprine 150mg

An otherwise healthy Behçet's patient on azathioprine 150mg daily who remains unvaccinated does not appear to face a substantially increased risk of acquiring COVID-19 infection compared to the general population, though they are at increased risk of serious infections generally and should be strongly encouraged to receive COVID-19 vaccination.

Understanding the Infection Risk

The FDA label for Imuran (azathioprine) clearly states that "patients receiving immunosuppressants, including Imuran, are at increased risk for bacterial, viral, fungal, protozoal, and opportunistic infections, including reactivation of latent infections" 1. However, this general warning about infection susceptibility does not translate directly to increased COVID-19 acquisition risk.

Evidence from Behçet's Disease Studies

Real-world data from Behçet's patients during the pandemic is reassuring:

  • A cohort study of 203 Behçet's patients found no increased frequency of SARS-CoV-2 infection compared to controls (18/56 tested positive vs 32/80 controls, p=0.321), with no differences in hospitalization length, lung involvement, ICU admissions, or mortality 2

  • Another study of 244 Behçet's patients reported a COVID-19 prevalence of 14.75%, though this was higher than Spain's general population at that time 3

  • A management study of 54 Behçet's patients during the pandemic found zero COVID-19 cases among those who continued their immunosuppressive treatments 4

Immunosuppression and COVID-19 Acquisition

A critical meta-analysis of 10,049 COVID-19 patients found that immunosuppressed individuals had an observed-to-expected ratio of 0.12 (95% CI: 0.05-0.27) for COVID-19 infection compared to the general population, suggesting immunosuppression does not increase acquisition risk 5.

Similarly, a large study of 1,052 SLE patients found no increased COVID-19 risk among those taking azathioprine specifically, with infection rates similar across treatment groups 6.

The Critical Distinction: Acquisition vs. Outcomes

The key issue is not getting infected—it's what happens after infection. The FDA warnings about serious infections refer to disease severity and complications, not necessarily increased susceptibility to initial infection 1.

Azathioprine-Specific Considerations

For your patient on 150mg azathioprine:

  • Dose-dependent risks: The FDA emphasizes that hematologic toxicities and infection risks are dose-related 1
  • TPMT status matters: Patients with intermediate or low TPMT activity face higher myelotoxicity risk, which could compound infection vulnerability 1
  • Monitoring is essential: Weekly CBC during month 1, twice monthly for months 2-3, then monthly monitoring is recommended 1

Vaccination as Risk Mitigation

Vaccination dramatically alters the risk equation. Recent large-scale data shows COVID-19 vaccination was associated with an almost halved risk of autoimmune complications (HR 0.514,95% CI 0.394-0.672), while COVID-19 infection increased risks 7.

For Behçet's patients specifically, vaccination improved outcomes substantially 3. The ACR guidance from 2020 supported continuing immunosuppressants while emphasizing infection prevention measures 8.

Clinical Recommendations

For your unvaccinated patient:

  1. Strongly recommend COVID-19 vaccination immediately - this is the single most important intervention
  2. Continue azathioprine unless contraindicated - stopping increases Behçet's flare risk without clear COVID-19 benefit 8, 9, 4
  3. Verify TPMT status if not already done - affects both azathioprine toxicity and infection risk 1
  4. Ensure proper monitoring - maintain regular CBC surveillance as immunosuppression increases risk of severe infection complications 1
  5. Counsel on infection prevention - social distancing, masking in high-risk settings, hand hygiene

Important Caveats

  • The evidence suggests acquisition risk is not substantially elevated, but severity of COVID-19 if infected may be worse in immunosuppressed patients 1
  • Combination with other immunosuppressants (especially high-dose steroids or JAK inhibitors) significantly increases poor outcome risk 10, 11
  • The pandemic phase matters - current circulating variants and population immunity differ from early pandemic data
  • Individual factors (age, comorbidities, TPMT status) modify risk beyond the azathioprine alone

The absence of vaccination represents the modifiable risk factor here, not the azathioprine itself.

References

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This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.