Threat of dying involving COVID-19 following an infection from Omicron relative to Delta

In a latest examine posted to the medRxiv* preprint server, an interdisciplinary crew of researchers from the UK (UK) performed a retrospective examine on a cohort of sufferers in England with extreme acute respiratory syndrome coronavirus 2 (SARS-CoV-2) optimistic take a look at outcomes.

Study: Risk of COVID-19 related deaths for SARS-CoV-2 Omicron (B.1.1.529) compared with Delta (B.1.617.2). Image Credit: Dmitry Demidovich/Shutterstock
Examine: Threat of COVID-19 associated deaths for SARS-CoV-2 Omicron (B.1.1.529) in contrast with Delta (B.1.617.2). Picture Credit score: Dmitry Demidovich/Shutterstock

They aimed to find out the relative threat of coronavirus illness 2019 (COVID-19)-induced mortality following SARS-CoV-2 Omicron an infection (B.1.1.539/BA.1) as in comparison with SARS-CoV-2 Delta an infection (B.1.617.2) utilizing dying registration information.

The Omicron variant, together with its sublineages BA.1, BA.2, and BA.3, has been reported to be extra transmissible than the Delta variant. With the fast emergence of Omicron variants, there may be an pressing must quantify the danger of COVID-19 deaths relative to different SARS-CoV-2 variants for healthcare necessities that may help the COVID-19 pandemic response planning.

Examine design

Within the present examine, the researchers collected information from the Workplace of Nationwide Statistics (ONS) Public Well being Information Asset (PHDA) that mixed the mortality data, 2011 census, Hospital Episode Statistics (HES), Common Apply Extraction Service (GPES), hint information, Nationwide Well being Service (NHS) and from Nationwide Immunisation Administration Service (NIMS).

The examine inhabitants included 1,035,163 people residing in England who had a optimistic COVID-19 polymerase chain response (PCR) take a look at between 1 December 2021 and 31 December 2021, when SARS-CoV-2 Delta and Omicron BA.1 variants have been co-circulating, with a uncommon circulation of the Omicron BA.2 variant.

COVID-19 dying as recognized by the Worldwide classification of disease- 10 (ICD-10) code talked about on the dying certificates was used as the first consequence. The SARS-CoV-2 variant sort detected as hint PCR optimistic assessments have been the publicity of curiosity.

General traits of the examine inhabitants have been summarized and stratified based on the kind of variant utilizing steady variables imply and share of categorical variables. The authors used a regression mannequin particular to Cox proportional hazard to find out the hazard ratio of mortality induced by COVID-19 for Omicron- and Delta-infected people.

They used 4 fashions:

  • Mannequin 1 – sequentially adjusted for intercourse, age, the standing of vaccination, and, former an infection;
  • Mannequin 2 – moreover adjusted for calendar time;
  • Mannequin 3 – with extra socio-economic options; and
  • Mannequin 4 – for pre-existing well being options.


The researchers observed that out of the studied population, 78.6% had Omicron infection, and 21.4% had Delta infection, which covered 36.7% of all positive COVID-19 tests in England in December 2021. In individuals with Omicron infection, there were 128 deaths attributable to COVID-19 and 53 deaths not attributable to COVID-19, while in Delta infection, the numbers were 189 and 28 deaths, respectively. For Omicron infection, the meantime from positive report to COVID-19-induced death was 13 days, while for Delta, it was 16 days.

In a fully adjusted model (Model 4) for Omicron infection, the risk of death due to COVID-19 was 67% lower than Delta infection. For the minimally adjusted model (Model 1), this risk was 78% lower for Omicron than Delta. In contrast, for Models 2 and 3, no relative difference was observed between Omicron and Delta infection mortality.

For Omicron and Delta infection, a higher reduction in COVID-19-induced mortality was observed for individuals under 18-59 years [hazard ratio (HR) =0.13] and 60-69 years (HR=0.14) of age as in comparison with the age group of 70 years and above (HR=0.45). A extra pronounced discount in mortality threat attributable to COVID-19 was noticed in males [(HR=0.25, 95% confidence interval (CI)] as in comparison with the females (HR=0.44, 95% CI).

The crew famous that whatever the age, administration with SARS-CoV-2 booster vaccination decreased the danger of mortality extra in Omicron an infection relative to Delta as in comparison with those that have obtained two doses of COVID-19 vaccine.

Curiously, the authors noticed that for all age teams, the COVID-19-induced mortality threat was decrease in Omicron an infection than Delta whatever the variety of comorbidities.


The findings of the examine illustrated a decrease threat of hospitalizations and deaths with Omicron-driven COVID-19 an infection as in comparison with that by Delta. The examine was the primary that assessed cause-specific COVID-19 deaths via dying certification to seize COVID-19-related deaths precisely.

Notably, the relative threat of COVID-19 deaths following Omicron versus Delta an infection was decrease in youthful people and the feminine inhabitants. The examine additionally highlighted the significance of the COVID-19 booster vaccination program as there was a extra pronounced discount within the threat of deaths involving COVID-19 within the inhabitants who’ve obtained a booster dose.

Nevertheless, the authors have warranted the necessity to examine the long-term consequence of infections like lengthy COVID-19 prevalence following Omicron an infection in comparison with Delta other than the mortality metric assessed on this examine.

*Essential discover

medRxiv publishes preliminary scientific stories that aren’t peer-reviewed and, due to this fact, shouldn’t be considered conclusive, information medical observe/health-related habits, or handled as established data.

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