Infection Risk Associated with High‐Efficacy Disease‐Modifying Agents in Multiple Sclerosis: A Retrospective Cohort Study

In patients with multiple sclerosis (MS), infections represent a significant concern, particularly given the immunomodulatory effects of disease-modifying agents (DMAs). High-efficacy DMAs (heDMAs) play a pivotal role in delaying MS progression, yet their use also raises concerns regarding the risk of infection. This study aimed to compare the infection risk with the use of heDMA and moderate-efficacy disease-modifying agents (meDMAs) in MS patients. This retrospective cohort study involved adult (18-64 years) MS patients with incident DMA use based on the 2015-2019 MarketScan Commercial Claims and Encounters Database. Patients initiating heDMAs (natalizumab, alemtuzumab, and ocrelizumab) or meDMAs (interferon beta-1a, interferon beta-1b, fingolimod, teriflunomide, dimethyl fumarate, and glatiramer acetate) were included. The outcomes of interest were comparative risk of overall infection, serious infection, and frequently reported types of infection. Adjusted hazard ratios (aHR) were estimated in inverse probability treatment weighting (IPTW) based on Cox proportional hazard models. Among 10,003 eligible incident DMA users, 22.92% of patients initiated heDMAs. The IPTW-CPH model revealed that patients with heDMAs were associated with a higher risk of serious infection (aHR: 1.24, 95% confidence interval (CI): 1.06-1.44) and urinary tract infection (UTI; aHR: 1.21, 95% CI: 1.14-1.30). Sensitivity analyses with different follow-up periods yielded consistent findings with the main analyses. In MS, heDMAs were associated with a greater risk of serious infection and UTI compared with meDMAs. These findings suggest the need to carefully monitor and manage the infection risk to optimize the use of heDMAs in MS.