Examining the COVID Omicron variant — is it actually less dangerous?

This article, about examining the dangers of the COVID-19 Omicron variant, is a reprint of a comment made by the user Dave Barton in response to the article published yesterday regarding the effectiveness of boosters. I thought what he wrote was too important to be hidden in a Disqus comment. It was slightly edited for readability and style purposes.

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Competing studies about the COVID-19 Omicron variant

There were dueling studies reported last week, which appear to contradict each other. Reuters reported on a preliminary UK study saying that the Omicron variant infections are no less dangerous than infections with earlier COVID-19 variants.

Forbes reported on that preliminary South African study saying that Omicron infections are less likely than previous (mostly Delta) infections to cause hospitalization, and among hospitalized patients, Omicron infections are less likely to cause severe disease than were previous variants.

So, how to reconcile those two reports? A closer look at the South African paper gives the likely answer. The South African study SOUNDS like good news, but it is not nearly as good as it sounds. In fact, it might NOT be good news at all.

That’s because much, or perhaps all, of the apparent reduction of risk of severe disease from Omicron is due to the fact that a high percentage of Omicron cases occur in people who already had some level of Covid-19 immunity, either through vaccination or through a previous infection.

In other words, what you’re seeing is a statistical artifact, due to the combination of two factors:

  1. Omicron is capable of breakthrough infections in a high percentage of people who already had a level of Covid-19 immunity; and
  2. Breakthrough infections in people who already have Covid-19 antibodies, either through vaccination or through previous infection, are usually fairly mild cases.
a sick man wiping his nose with tissue
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So, what does this all mean?

Q: How can we tell that much, or perhaps all, or the apparent reduction of risk of severe disease is due to the fact that a high percentage of Omicron variant cases occur in people who already have a level of COVID-19 immunity, either through vaccination or through a previous infection?

A: Read the “RESULTS” and “CONCLUSION” sections of the preprint.

(Note: “SGTF” refers to Omicron infections; “non-SGTF” are other variants, mostly Delta.)

RESULTS:

From 1 October through 6 December 2021, 161,328 COVID-19 cases were reported nationally; 38,282 were tested using TaqPath PCR and 29,721 SGTF infections were identified. The proportion of SGTF infections increased from 3% in early October (week 39) to 98% in early December (week 48). On multivariable analysis, after controlling for factors associated with hospitalisation, individuals with SGTF infection had lower odds of being admitted to hospital compared to non-SGTF infections (adjusted odds ratio (aOR) 0.2, 95% confidence interval (CI) 0.1-0.3). Among hospitalised individuals, after controlling for factors associated with severe disease, the odds of severe disease did not differ between SGTF-infected individuals compared to non-SGTF individuals diagnosed during the same time period (aOR 0.7, 95% CI 0.3-1.4). Compared to earlier Delta infections, after controlling for factors associated with severe disease, SGTF-infected individuals had a lower odds of severe disease (aOR 0.3, 95% CI 0.2-0.5).

CONCLUSION:

Early analyses suggest a reduced risk of hospitalisation among SGTF-infected individuals when compared to non-SGTF infected individuals in the same time period. Once hospitalised, risk of severe disease was similar for SGTF- and non-SGTF infected individuals, while SGTF-infected individuals had a reduced risk of severe disease when compared to earlier Delta-infected individuals. Some of this reduction is likely a result of high population immunity.

Did you notice it?

Pay attention to the second sentence of the “CONCLUSION” section: 

Once hospitalised, risk of severe disease was similar for SGTF- and non-SGTF infected individuals, while SGTF-infected individuals had a reduced risk of severe disease when compared to earlier Delta-infected individuals.

So, why do you think hospitalized Omicron and non-Omicron patients had the same risk of severe disease, currently, but earlier infections had a higher risk of severe disease? What is the difference between current infections and earlier infections?

One factor might be that treatment protocols are improving.

Another factor that could account for the difference: a higher percentage of recent cases are “breakthrough” cases, in people who already had some level of immunity, either from vaccination or from the previous disease.

The authors obviously recognized this possibility, as reflected in their final sentence in the “CONCLUSION” section: 

Some of this reduction is likely a result of high population immunity.

It is probable that the apparent reduction of risk of hospitalization from Omicron is also due mostly or entirely to the high percentage of breakthrough cases.

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Summary

It is clear that Omicron is far more transmissible than previous variants, at least in part because it causes many breakthrough infections in people who already had Covid-19 antibodies. That is BAD news.

It is unclear whether Omicron is intrinsically less dangerous than earlier Covid-19 variants, or just appears to be less dangerous because it causes so many breakthrough infections, and breakthrough infections are mostly mild.

So, from the South African study, WE CANNOT TELL whether Omicron infection is more or less dangerous than earlier variants, for unvaccinated people, with no COVID-19 previous infection.

But there is ONE other conclusion that is CRYSTAL CLEAR — unless you’ve acquired immunity “the hard way” (by a previous infection), to reduce your risk of serious disease it is critically important to GET VACCINATED ASAP!!!

PLEASE, friends…
Get smart.
Get vaccinated!


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The Original Skeptical Raptor
Chief Executive Officer at SkepticalRaptor
Lifetime lover of science, especially biomedical research. Spent years in academics, business development, research, and traveling the world shilling for Big Pharma. I love sports, mostly college basketball and football, hockey, and baseball. I enjoy great food and intelligent conversation. And a delicious morning coffee!