Epidemiological Characteristics and Severity of Omicron Variant Cases in the Aphp Critical Care Units

Abstract

Importance Information about the severity of Omicron is scarce. Objective To report the respective risk of ICU admission in patients hospitalized with Delta and Omicron variants and to compare the characteristics and disease severity of critically ill patients infected with both variants according to vaccination status. Design Analysis from the APHP database, called Reality, prospectively recording the following information in consecutive patients admitted in the ICU for COVID-19: age, sex, type of variant, immunosuppression, vaccination, pneumonia, need for invasive mechanical ventilation, time between symptom onset and ICU admission, and in-ICU mortality. Retrospective analysis on an administrative database, Systeme Information pour le Suivi des Victimes (SI-VIC), which lists hospitalized COVID-19 patients. Setting 39 hospitals in the Paris area from APHP group. Participants Patients hospitalized from December 1, 2021 to January 18, 2022 for COVID-19. Main outcomes and measures Risk of ICU admission was evaluated in 3761 patients and Omicron cases were compared to Delta cases in the ICU in 888 consecutive patients. Results On January 18, 45% of patients in the ICU and 63.8% of patients in conventional hospital units were infected with the Omicron variant (p < 0.001). The risk of ICU admission with Omicron was reduced by 64% than with Delta (9.3% versus 25.8% of cases, respectively, p < 0.001). In critically ill patients, 400 had the Delta variant, 229 the Omicron variant, 98 had an uninformative variant screening test and 161 did not have information on variant screening test. 747 patients (84.1%) were admitted for pneumonia. Compared to patients infected with Delta, Omicron patients were more vaccinated (p<0.001), even with 3 doses, more immunocompromised (p<0.001), less admitted for pneumonia (p<0.001), especially when vaccinated (62.1% in vaccinated versus 80.7% in unvaccinated, p<0.001), and less invasively ventilated (p=0.02). Similar results were found in the subgroup of pneumonia but Omicron cases were older. Unadjusted in-ICU mortality did not differ between Omicron and Delta cases, neither in the overall population (20.0% versus 27.9%, p = 0.08), nor in patients with pneumonia (31.6% versus 29.7%, respectively) where adjusted in-ICU mortality did not differ according to the variant (HR 1.43 95%CI [0.89;2.29], p=0.14). Conclusion and relevance Compared to the Delta variant, the Omicron variant is less likely to result in ICU admission and less likely to be associated with pneumonia. However, when patients with the Omicron variant are admitted for pneumonia, the severity seems similar to that of patients with the Delta variant, with more immunocompromised and vaccinated patients and no difference in adjusted in-ICU mortality. Further studies are needed to confirm our results.

Milder disease trajectory among COVID-19 patients hospitalised with the SARS-CoV-2 Omicron variant compared with the Delta variant in Norway

“…This supports the growing evidence of reduced disease severity among those infected with Omicron [2,4–8]. Results from similar studies in South Africa, the United States and France have also reported a reduction in LoS, risk of ICU admission and/or death among Omicron patients compared with Delta patients [9–12].…”

“…Results from similar studies in South Africa, the United States and France have also reported a reduction in LoS, risk of ICU admission and/or death among Omicron patients compared with Delta patients [9][10][11][12].…”

Milder disease trajectory among COVID-19 patients hospitalised with the SARS-CoV-2 Omicron variant compared with the Delta variant in Norway

“…This supports the growing evidence of reduced disease severity among those infected with Omicron (2;4-8). Results from similar studies in South Africa, USA and France have also reported a reduction in the median LoS, risk of ICU admission and/or death among Omicron patients compared to Delta patients (9-12).…”

Characterization and antiviral susceptibility of SARS-CoV-2 Omicron BA.2

“…Given that the amino acid sequence of the S protein of the recombinant BA.2 virus that these authors tested is the same as that of the BA.2 isolate that we tested, differences at locations other than the S gene could have epistatic or independent effects that offset differences in the pathogenic potential of the S gene 44 . Omicron variants are less likely than Delta variants to be associated with pneumonia in human patients with COVID-19 45 . We observed that BA.2 infection in the lung was less pathogenic in mice and hamsters than SARS-CoV-2 strains from early in the pandemic (Figs.…”