Further, we demonstrated the usefulness of DNAm surrogate biomarkers in investigating COVID-19 susceptibility and severity, showing that DNAmBMI was associated with case–control status, while measured BMI was not (Additional file 1; Additional file 2: Table S2), and that DNAmCRP outperformed blood measured CRP in predicting disease severity (Additional file 1; Additional file 2: Table S2). This evidence concerns the gene CRP and COVID-19.