Abstract Older adults are highly vulnerable to severe COVID‐19. Unlike our previous work on broad immunosenescence, this review focuses on peripheral hematological markers as practical indicators of risk. To examine lymphopenia, neutrophilia, and the neutrophil‐to‐lymphocyte ratio (NLR) as clinically accessible markers of immune aging and COVID‐19 severity in older adults. Literature search of PubMed, Scopus, and Web of Science (up to 2025) for studies on aging, immunosenescence, lymphopenia, neutrophilia, NLR, and COVID‐19. These markers consistently correlate with worse COVID‐19 outcomes; NLR is a simple, reliable indicator of immune dysregulation, systemic inflammation, and mortality risk. Lymphopenia, neutrophilia, and elevated NLR are low‐cost, readily measurable markers associated with COVID‐19 severity, highlighting their prognostic value and complementing prior immunosenescence research.
Gasmi et al. (Sun,) studied this question.