Résumé
BackgroundA novel variant of SARS-CoV-2, the Delta variant of concern (VOC), on disease severity is very unclear. In this retrospective study, we compared the clinical characteristics and the outcomes of patients infected with the Delta VOC and with wild-type strains during the local outbreak in Xi'an and Wuhan, China.MethodsThe clinical information pertaining to the 2927 cases (between February 10 and March 8, 2020) infected with wild-type strains and the 993 cases (between December 22, 2021and February 17, 2022) infected with the Delta VOC were extracted. The clinical characteristics and outcomes were compared the cohort of wild-type infection with the cohort of Delta VOC.ResultsAmong patients younger than 18 years old, the proportion of patients infected with the Delta VOC was significantly higher than that of patients infected with wild-type strains (12.2% vs. 0.3%). In cases with mild and moderate illness, the proportion of patients was higher in the Delta VOC group than that in the wild-type strain (40.9% and 56.6% vs. 0.70% and 3.10%). However, in severe and critical patients, the proportion of patients was significantly less in the Delta VOC group than that in the wild-type strain (1.6% and 0.9% vs. 24.2% and 72.0%). In cases with severe or critical illness, and in the Delta VOC cohort or the wild-type cohort, the prognosis of patients with lymphocytes blood levels that gradually rising is good after treatment, while the prognosis of patients with lymphocytes blood levels that remain low is poor and even death(p<0.001). The Cox regression analysis revealed that the infection with the lineage of the wide-type strain had a higher risk than the Delta VOC in deteriorating to critical illness (hazards ratio 2.54[95%CI 1.279–5.026]; p = 0.008).ConclusionsUnder the two different anti-epidemic situations and anti-epidemic strategies, infection with the Delta VOC is characterized by younger patients, milder illness, and decreased risk of disease prognosis, compared with the SARS-CoV-2 wild-type lineage; lymphopenia is an effective predictor of deterioration in patients with Delta VOC and wild-type strains, calling for clinicians to understand of characteristics of them according to the different anti-epidemic situations and anti-epidemic strategies, and to guide clinical decision-making.