SARS-CoV-2-associated mortality with a principal cause other than COVID-19 during the Omicron epidemic in France and detection and treatment of Omicron infections in associated complications

BackgroundWith the emergence of the Omicron variant, an increasing proportion of SARS-CoV-2 associated deaths have a principal cause of death other than COVID-19. In France, between Nov. 1, 2021 --July 31, 2022, in addition to 33,353 deaths with the principal cause of COVID-19, there were 9,638 deaths with a confirmed SARS-CoV-2 infection with a principal cause of death other than COVID-19 (as well as SARS-CoV-2-associated deaths with an undetected SARS-CoV-2 infection). MethodsWe examined the relation between mortality for COVID-19, mortality for other causes, and ICU admissions with a SARS-CoV-2-infection in adults aged over 60y in France. ResultsThe number of deaths with principal causes other than COVID-19 in France between July 2021-June 2022 was greater than the corresponding number between July 2020-June 2021 by 20,860 (95% CI (11241,30421)) after adjusting for pre-pandemic trends in mortality (compared to the increase of 3,078 in the number of deaths with a SARS-CoV-2 infection with principal causes other than COVID-19 between the two time periods). During the period of Omicron circulation (Nov. 1, 2021 - Nov. 13, 2022), there was a strong association between the rates of ICU admission with a SARS-CoV-2 infection in adults aged over 60y and (a) rates of COVID-19 deaths (correlation=0.96 (0.92,0.97)); (b) rates of mortality with principal causes other than COVID-19 (correlation=0.89 (0.82,0.94)). Proportions of ICU admissions for causes other than COVID-19 among all ICU admissions with a SARS-CoV-2 infection in older adults were lower during the periods when rates of COVID-19 disease in the community were higher. ConclusionsThe significant increase in mortality with principal causes other than COVID-19, as well as the decreases in the proportions of ICU admissions for causes other than COVID-19 among all ICU admissions with a SARS-CoV-2 infection in older adults during the periods when rates of COVID-19 disease in the community were higher suggest under-detection of Omicron infections in associated complications that did not manifest themselves as COVID-19, which is related to the treatment of SARS-CoV-2 infection in those complications.