Study Links Lymphocyte Levels to Severe COVID-19 Outcomes

March 18, 2026
COVID-19

A recent publication in BMC Infectious Diseases highlights the importance of absolute lymphocyte counts in understanding the severity and recovery patterns of hospitalized COVID‑19 patients.

The findings draw on data from the STRIVE Network’s Therapeutic Intervention for Inpatients with COVID‑19 (TICO) clinical trial platform, to which Timothy Hatlen, MD served as the Lundquist Institute’s local Principal Investigator contributing research participants.

Project Overview

The study examined Day 0 lymphopenia—defined as an absolute lymphocyte count (ALC) below 0.9 cells/µL—and severe lymphopenia (ALC below 0.5 cells/µL). Both were associated with higher mortality and slower recovery. Persistent lymphopenia by Day 5 was linked to increased mortality and secondary infections, while both persistent and newly developed lymphopenia were associated with impaired recovery.
Factors tied to persistent or new lymphopenia included older age, prior immunosuppression, heart failure, aspirin use, normal BMI, and biomarkers indicating organ damage or ineffective immune response, such as elevated IL‑6 and viral nucleocapsid antigen levels.

Impact of the Research

Overall, lymphopenia—especially when persistent or newly observed during hospitalization—was a strong predictor of severe COVID‑19 outcomes. The full study is available at: https://doi.org/10.1186/s12879-024-10428-7

Dr Hatlen and the STRIVE Network will continue to improve the understanding of therapeutic Intervention for inpatients with infectious disease. The Divisions of Infectious Diseases and HIV Medicine are proud to support Dr. Hatlen’s efforts to improve patient outcomes and save lives. For more information on Dr. Hatlen’s research or about the Division of Infectious Diseases and HIV Medicine at The Lundquist Institute, please visit : Lundquist.org/Timothy Hatlen MD