Introduction: SARS Cov2 infection still represents a real threat whose clinical severity results from an inadequate immuno-inflammatory reaction. The objective of our study was to determine the prognostic interest of the value of CRP and the rate of lymphocytes in the management of patients contaminated by SARS-Cov2. Material And Methods: This is a prospective, descriptive and analytical study of interest to patients with severe COVID-19, admitted to medical intensive care at the Oued Eddahab military hospital, for a period of one year. The biological parameters were analyzed on admission and during the stay in intensive care. The ROC curve was used to determine the sensitivity and specificity of CRP and lymphocytes as well as their optimal predictive threshold values. Results: 32 patients were included in our study. The average age of admissions was 65 years ± 12.38 with a sex ratio of 5.4 in favor of men. The optimal predictive threshold for the severity found was 147mg/l for CRP with a sensitization of 95% and a specificity of 83.3%, and 807/mm3 for lymphocytes with a sensitivity of 91.7% and a specificity of 95%. The odds ratio (OR) found for CRP and lymphocytes was > 1. Conclusion: The CRP and the level of lymphocytes at the threshold defined above are risk factors for the severity of Sars-Cov2 infection.