EPIDEMIOLOGICAL CHARACTERISTICS AND SEVERITY OF OMICRON VARIANT CASES IN THE APHP CRITICAL CARE UNITS
Authors: Vieillard-Baron Antoine , Flicoteaux Rémi , Salmona Maud , Annane Djillali , Ayed Soufia , Azoulay Elie , Bellaiche Raphael , Beloucif Sadek , Berti Enora , Bertier Astrid , Besset Sébastien , Bret Marlène , Cariou Alain , Carpentier Christophe , Chaouch Oussama , Chariot Appoline , Charron Cyril , Charpentier Julien , Cheurfa Cherifa , Cholley Bernard , Clerc Sébastien , Combes Alain , Chousterman Benjamin , Cohen Yves , Constantin Jean-Michel , Damoisel Charles , Darmon Michael , Degos Vincent , D’Ableiges Bertrand De Maupeou , Demeret Sophie , Montmollin Etienne De , Demoule Alexandre , Depret Francois , Diehl Jean-Luc , Djibré Michel , Do Chung-Hi , Dudoignon Emmanuel , Duranteau Jacques , Fartoukh Muriel , Fieux Fabienne , Gayat Etienne , Gennequin Mael , Guidet Bertrand , Gutton Christophe , Hamada Sophie , Heming Nicholas , Jouffroy Romain , Keita-Meyer Hawa , Langeron Olivier , Lortat-Jacob Brice , Marey Jonathan , Mebazaa Alexandre , Megarbane Bruno , Mekontso-Dessap Armand , Mira Jean-Paul , Molle Julie , Mongardon Nicolas , Montravers Philippe , Morelot-Panzini Capucine , Nemlaghi Safaa , Nguyen Bao-long , Parrot Antoine , Pasqualotto Romain , Peron Nicolas , Picard Lucile , de Chambrun Marc Pineton , Planquette Benjamin , Plaud Benoit , Pons Stéphanie , Quesnel Christophe , Raphalen Jean-Herlé , Razazi Keyvan , Ricard Jean-Damien , Roche Anne , Rohaut Benjamin , Roux Damien , Savale Laurent , Sobotka Jennifer , Teboul Jean-Louis , Timsit Jean-François , Voiriot Guillaume , Weiss Emmanuel , Wildenberg Lucille , Zogheib Elie , Riou Bruno , Batteux Frédéric 
Published: January 2022

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, 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, “Système d’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.