Bouzid et al., Outcomes of Omicron sub-lineages BA.1.1 and BA.2 infection compared with the sub-lineage BA.1 infection in emergency departments’ patients, Clin Microbiol Infect, 2023

D Bouzid, T Kapfer, S Marot, V Ing, V M Ferré, A Chauvin, J Le Goff, S Ellouze, M Salmona, C Hermand, A Bourg, A Schnuriger, F Fémy, M Nguyen Van Tinh, S Brichler, D Veyer, P Le Borgne, S Fafi-Kremer, A S L’Honneur, C Augustin, T Simon, M Cachanado, IMProving Emergency Care (IMPEC) FHU authors group, Y Freund

Clin Microbiol Infect, 2023 Apr, doi: 10.1016/j.cmi.2023.01.001


The Omicron SARS-CoV-2 variant of concern (B.1.1.529) was first reported in South Africa in November, 2021. Several reports indicated that the infection with Omicron (BA.1 sub-lineage) was associated with a lower risk of hospitalization and severe outcomes compared with delta (B.1.617.2) variant infection [[1],[2]]. During 2022, the Omicron variant was still the dominant circulating variant, and has been divided into several sub-lineages, BA.1.1 and BA.2, then later BA.3, BA.4, and BA.5 [[3]]. Data on the clinical patterns and outcomes of Omicron sub-lineages infections are still scarce [[4],[5]]. This report compares the in-hospital outcomes of emergency department (ED) patients infected with BA.1 vs. the BA.2 and BA1.1 sub-lineages.This study was a retrospective analysis of prospective routinely collected data of individual patients in 10 EDs in France, caring for adult patients from January 3, 2022 to May 22, 2022. The study was approved by the ethics committee of Sorbonne Université (CER-2022-044), Paris, France.All patients with positive reverse transcriptase polymerase chain reaction (RT-PCR) test results for SARS-CoV-2 followed by a variant determination were screened, and patients with BA.1, BA1.1, and BA.2 infection were included. Using previously described methods, baseline clinical and biological characteristics of patients with BA.1 and other sub-lineages of Omicron SARS-CoV-2 infections in the ED were compared [[1]]. Primary endpoints included intensive care unit (ICU) hospitalization, mechanical ventilation, and death. Secondary endpoints included vaccine status. Differences and 95% CIs were calculated using the Wald method, with continuity correction for categorical variables and using normal approximation or the Brookmeyer and Crowley method for continuous variables, depending on their distribution. Logistic regression modelling was used to study the relationship between SARS-CoV-2 variant and outcomes, adjusted to age, sex, hypertension, obesity, diabetes, chronic respiratory disease, chronic kidney disease, immunosuppression, number of vaccine doses, and centre. Because BA1.1 is a sub-lineage of BA.1, a sensitivity analysis compared BA.2 with either BA.1 or BA.1.1). Results are expressed as differences and 2-sided 95% CIs. Analyses were done with SAS, version 9.4 (SAS Institute).A total of 1012 patients were included. The median age was 69 (interquartile range, 47–83 years), and 46% were women.