Omicron Today

Top Science News this Week

Below are five articles that stand out as being among the most important regarding Omicron this week.

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Epidemiological characterisation of the first 785 SARS-CoV-2 Omicron variant cases in Denmark, December 2021

Published in: Eurosurveillance  Volume 26, Issue 50, 16/Dec/2021

Denmark, as of December 9, 2021. Denmark has one of the highest RT-PCR testing capacities in the world and screens all positive RT-PCR tests with an Omicron-specific PCR – allowing screening for Omicron.

There have been 785 SARS-CoV-2 Omicron variant cases identified in Denmark. The earliest Omicron cases in Denmark occurred before South Africa announced the emergence of this variant. Most cases were fully (76%) or booster-vaccinated (7.1%); 34 (4.3%) had a previous SARS-CoV-2 infection. The majority of cases with available information reported symptoms (509/666; 76%) and most were infected in Denmark (588/644; 91%).

One in five cases cannot be linked to previous cases, indicating widespread community transmission.

Nine cases have been hospitalized, one required intensive care and no deaths have been registered.

Highlights:

·      1.2% of cases have been hospitalized

·      0.3% in intensive care

·      0% deaths.

·      83% were fully or booster vaccinated, 17% not vaccinated (including 2.6 vaccine started)

·      4.3% had previous SARS-CoV-2 infection

·      91% have no travel history, 9% reported travel

My take: this study is important because although there are studies and spokespeople from South Africa stating similar results, the Danish population in terms of age, body weight, life expectancy, etc. is more similar demographically to the US population. This Danish study suggests that Omicron will affect the American population similarly.

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Covid-19: Runny nose, headache, and fatigue are commonest symptoms of omicron, early data show

Published in: BMJ 2021; 375 doi: https://doi.org/10.1136/bmj.n3103 (16 December 2021)

This College of London study shows that the top five symptoms reported for omicron infection are runny nose, headache, fatigue (either mild or severe), sneezing, and sore throat.  This study is in line with what the US Centers for Disease Control and Prevention, the World Health Organization, and European countries such as Spain and France had all updated their advice. The authors recommend that the National Health Service should also amend their advice on Omicron.

This study is important because it is more evidence that 1) symptoms are more mild and 2) more evidence that Omicron has evolved to infect the upper respiratory system more readily than the lower respiratory tissue (see my earlier substack article on this topic).

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Omicron SARS-CoV-2 variant: Unique features and their impact on pre-existing antibodies

J Autoimmun 2021 Dec 13;126:102779. doi: 10.1016/j.jaut.2021.102779. Online ahead of print.

Highlights

•Phylogenetically SARS-CoV-2 Omicron variant is closely related to the Gamma variant.

•There are a total of 46 high prevalent mutations throughout the SARS-CoV-2 Omicron variant.

•Twenty three of the 46 mutations, which is more than any previously emerged variant belong to the S protein.

•Twenty-three of the 46 mutations are a markedly high number of mutations than has been previously reported for the S protein of other emerging variants.

•A significant number of mutations are at the antibody binding surface of S protein.

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Covid-19: Omicron is causing more infections but fewer hospital admissions than delta, South African data show

BMJ 2021; 375 doi: https://doi.org/10.1136/bmj.n3104 (Published 16 December 2021)Cite this as: BMJ 2021;375:n3104

Data from South Africa’s largest private health insurer suggest that omicron is spreading faster than any previous coronavirus variant and showing signs of immune escape, with both vaccinated and previously infected people more at risk than in previous waves.

More than 90% of newly sequenced infections in South Africa now involve the omicron variant, and as it displaced delta.

This data has not been peer reviewed. 

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HKUMed finds Omicron SARS-CoV-2 can infect faster and better than Delta in human bronchus but with less severe infection in lung

Pre-release of preprint from HKUMed: this paper is currently undergoing peer review

This papers shows that Omicron appears to be associated with three broad characteristics: Vaccine escape (resistance), increased viral replication and reduced disease. In contrast, the preceding dominant variant (Delta) is also associated with vaccine escape, increased viral replication, and increased disease severity compared to preceding dominant circulating variants. 

My take: This study presented the data that allowed me to formulate the hypothesis that Omicron may have now evolved to replicate more in our upper respiratory airway, and less in the deep part of our lung tissues due to shifts in receptor specificity. In other diseases, like influenza, replication in upper respiratory airways is associated with less severe disease.