Thiopurines and Infection Risk in IBD

Research published on February 13, 2026, indicates that patients with inflammatory bowel disease (IBD) who initiate thiopurine therapy experience an increased risk of mild infections, particularly viral and upper respiratory tract infections. However, the study found no significant increase in the risk of moderate-to-severe infections associated with the treatment.

The findings suggest that while thiopurines remain relatively safe in terms of overall infection risk, the rise in mild infections creates a clinically relevant burden that may impact patient adherence to therapy and overall quality of life.

Swedish Study on Thiopurine-Naive Patients

The data was derived from a study conducted at Skåne University Hospital in Sweden, which included 244 thiopurine-naive adults with IBD. These patients initiated thiopurine therapy between January 1, 2015, and December 31, 2022.

Researchers identified patients through the Swedish IBD Quality Register and reviewed medical records from both primary and secondary care. Infection incidence was tracked starting from two years before the initiation of thiopurine therapy and continued until the therapy was discontinued, switched, or until December 31, 2023.

Analysis of Infection Incidence Rates

The study observed that the incidence rate (IR) of any infection rose from 22.4 (95% CI: 18.2-27.6) to 31.8 (95% CI: 26.7-37.9) per 100 person-years following the start of thiopurine treatment.

The incidence rate ratio (IRR) for various types of infections showed a distinct pattern of risk:

• Any infection: IRR = 1.4 (95% CI: 1.2-1.7)
• Mild infections: IRR = 1.8 (95% CI: 1.2-2.5)
• Viral infections: IRR = 2.3 (95% CI: 1.6-3.3)
• Upper respiratory tract infections: IRR = 2.4 (95% CI: 1.5-3.8)

In contrast, the risk for moderate-to-severe infections did not show a significant increase, with an IRR of 1.2 (95% CI: 0.9-1.5).

Clinical Implications and Global Context

The increase in mild viral respiratory infections is noted as a significant factor for clinicians and patients to consider. Although these infections are not severe, their frequency can influence how patients perceive their treatment and their willingness to continue the medication.

The continued use of thiopurines remains critical in certain global regions. In developing countries, biologics are used by only a small proportion of patients with IBD due to high costs and the increased risk of tuberculosis reactivation.

Because of these limitations regarding biologic therapies, thiopurines are essential for the optimal management of IBD patients in those regions.

While thiopurines appear relatively safe in terms of infection risk, the rise in mild infections remains a clinically relevant burden, potentially affecting quality of life and adherence.

Study published February 13, 2026, via PubMed