The infection risks of JAK inhibition.

Data currently available for the licensed JAKi show an increased risk of infection across the class compared to placebo, most commonly affecting the respiratory and urinary tracts, nasopharynx and skin. This risk is dose-dependent, but similar at the licensed JAKi doses to that seen with biologic therapies. The risk is compounded by other risk factors for infection such as age and steroid co-prescription. Herpes zoster reactivation is more common with JAKi compared to other targeted immune modulation, making screening for varicella exposure and judicious vaccination in appropriate cohorts an advisable strategy. Crucially, these small risk increases must be balanced against the known harms (including infection) of uncontrolled autoimmune disease. JAKi are a safe and potentially transformative treatment when used for appropriately selected patients.