Reduced Risk of Hospitalisation Associated With Infection With SARS-CoV-2 Omicron Relative to Delta: A Danish Cohort Study

Comparative analysis of the risks of hospitalisation and death associated with SARS-CoV-2 omicron (B.1.1.529) and delta (B.1.617.2) variants in England: a cohort study

“…Our results support those of a number of other studies which have reported that omicron has substantially reduced overall severity compared with delta. 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 However, relatively few studies have examined how the reduction in severity might vary with age. A US study 12 compared 3-day follow-up outcomes in individuals younger than 5 years in the previous delta epidemic wave with those in the ongoing omicron epidemic and found a relative risk of emergency department attendance of 0·71 (95% CI 0·66–0·75) and a relative risk of admission of 0·33 (0·26–0·43).…”

“…A second study involved a contemporaneous comparison of omicron and delta (distinguished via S-gene target failure) cases in southern California 10 and estimated unadjusted odds ratios for hospitalisation in 0–17-year-olds of 0·70 (95% CI 0·12–3·97) and 0·94 (0·26–3·42) using denominators of only outpatient tests and both inpatient and outpatient tests, respectively. A Danish study 11 estimated a relative risk of hospitalisation of 1·59 (1·09–2·32) in 0–19-year-olds, although this estimate was based on only 31 hospitalisations in that age group. Last, a Norwegian cohort study 13 found no significant differences by age in the relative risk of hospitalisation for people younger than 75 years, with a point estimate for individuals younger than 30 years of 0·24 (95% CI 0·09–0·60); the study had insufficient power to stratify that age group further.…”

“…A number of studies have indicated that the clinical severity of infection is lower for omicron than for delta. 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 Vaccine effectiveness estimates show reduced protection against symptomatic infection for omicron compared with that of delta, with this protection being low after the primary course, but moderate against symptomatic infection and high against hospitalisation after a booster dose. 18 In England, such estimates have been obtained in a context of high vaccination coverage.…”

Critical View on the Importance of Host Defense Strategies on Virus Distribution of Bee Viruses: What Can We Learn from SARS-CoV-2 Variants?

“…Variant shifts have also been observed during the SARS-CoV-2 pandemic, and currently the Omicron SARS-CoV-2 (B.1.1.529) variant has replaced the more severe and less transmissible Delta SARS-CoV-2 (B.1.617.2) variant [ 82 ]. Here, several studies have found that the Omicron variant has a lower hospitalization rate as well as decreased risks of severe clinical symptoms compared to the Delta variant [ 83 , 84 , 85 , 86 ]. However, due to the higher transmissibility of the Omicron variant, i.e., reaching and infecting more people, some countries report a net increase in absolute numbers of hospitalization compared to the Delta variant, yet still associated with a lower clinical severity [ 87 ].…”

Omicron: fewer adverse outcomes come with new dangers

“…Initial omicron studies included fewer cases than included by Nyberg and colleagues 6 because analysis occurred earlier in the outbreak, such as in South Africa, 7 Denmark, 8 Norway, 9 or Scotland, 10 or were restricted to smaller regions and hospitals. Nyberg and colleagues have conducted the first large scale severity study based on 1 516 702 individuals with COVID-19, of whom 1 067 859 were infected with the omicron variant, using a mix of epidemiological and genetic molecular data.…”