Association of Measles IgG Antibody Titers with Thoracic CT Severity in Hospitalized Patients with COVID-19

<title>Abstract</title> <p>Background Coronavirus disease 2019 (COVID-19) has a broad clinical spectrum ranging from mild respiratory symptoms to severe pneumonia and death. Previous studies have suggested that pre-existing immunity against measles may influence immune responses during SARS-CoV-2 infection; however, the clinical significance of anti-measles IgG titers in COVID-19 remains unclear. Therefore, we aimed to investigate the association between anti-measles IgG titers, clinical severity, COVID-19 Mortality Rate (CMR) score, intensive care unit (ICU) requirement, and mortality in hospitalized COVID-19 patients. Material and Methods This cross-sectional study included 153 hospitalized COVID-19 patients (86 males and 67 females). Disease severity was classified according to the NIH COVID-19 Treatment Guidelines. Anti-measles IgG levels were measured using an indirect ELISA assay. Mortality risk was assessed using the COVID-19 Mortality Rate (CMR) score. Results Higher anti-measles IgG titers were observed in patients with severe COVID-19 and severe thoracic CT involvement compared with patients with milder disease. Anti-measles IgG titers were significantly higher in patients with severe CT involvement compared with those with non-severe involvement and remained independently associated with severe thoracic CT involvement after adjustment for clinical and laboratory parameters. However, anti-measles IgG levels were not independently associated with mortality or ICU admission. Non-survivors were older, had longer hospital stays, higher CMR scores, and lower admission SpO₂ levels compared with survivors. Similarly, patients requiring ICU admission had higher CMR scores and more severe thoracic CT involvement. Conclusion Higher anti-measles IgG titers were independently associated with severe thoracic CT involvement in hospitalized COVID-19 patients. These findings suggest that anti-measles IgG levels may represent a potential immunological marker associated with pulmonary disease severity rather than a direct marker of mortality risk. Further prospective studies with larger populations are needed to clarify the clinical significance of anti-measles IgG responses in COVID-19.</p>