What do we Know about Omicron and Hospitalizations?

Pascal LapointeThe Rumor Detector

Agence Science-Presse (www.sciencepresse.qc.ca)

At this point, we know that the Omicron variant spreads faster than its predecessors. But all the worry is about the hospitalization rate. Does Omicron cause a lot of serious cases leading to hospitalization? The Rumor Detector looks at what we know…

It’s a simple mathematical calculation: in a fictitious scenario in which Omicron is three times more transmissible than delta but three times less severe, the hospitalization rate will remain stable. But if Omicron is two times less severe, or just as severe, hospitalizations will go way up two to three weeks after case numbers rise.

1) In South Africa, the first bits of news of December 14th have been encouraging. According to a report published by the insurance company Discovery Health, a double vaccination seems to offer weak protection against Omicron (33%) but a relatively strong protection against hospitalization on the order of 70%. The 70% figure was used by INESSS in Québec on December 15th to make its projections on the rise of hospitalizations over the holiday season. They project a disturbing rise, but one within the capacity of hospitals to manage.  

Moreover, reports from South African hospitals note that the country isn’t being faced with a worrying rise in hospitalizations despite a huge increase in the number of COVID cases. But note that the population of South Africa is much younger that those of European and North American nations. The average age of the population studied by Discovery Health is 34.

Indeed, since last week, the curve of cases in the province of Gauteng — where Omicron was first detected – has started to dip. We don’t know if this means that the Omicron wave doesn’t last long, or if it started in Gauteng before it was first detected there. That’s why experts are taking a very close look at how Omicron acts in the first European countries to have been affected.

2) In Denmark, the first data published December 13th on hospitalizations brought mixed results. Later results are encouraging. As of December 20th, about 22,000 cases of Omicron have been identified since November 22nd, 13,000 of which were identified since December 14th, resulting in only 40 hospitalizations. Note that there might be a delay of two weeks between the infection curve rising and hospitalizations.  

3) In Great Britain, a study by Imperial College London published on December 16th, a model based on lab analysis, reached two conclusions: on the one hand, the protection offered against Omicron by a double Pfizer vaccination is weak, and a third booster shot is required; but on the other hand, the protection offered against serious infections (those leading to hospitalizations) remain high (80%, versus 95% for Delta).  

4) During a World Health Organization meeting on December 15th, several international experts presented data stating that antibodies react less well to Omicron than to other COVID variants. This means that vaccines still leave people vulnerable to infection. But T cells, another mechanism of our immune system, continue to react well to Omicron, protecting infected people from the worse effects of COVID, and therefore limiting the risks of hospitalization.  

An international team published similar conclusions on December 14th concerning six vaccines, including the Chinese Sinopharm and the Russian Sputnik.  

In Denmark and Great Britain, experts seemed to agree that a third booster shot greatly increases protection. But Omicron will have time to spread throughout the population before they can get a booster, except for perhaps the elderly and those more vulnerable to infections.

Finally, it should be noted that the hospitalization rate is more complex to predict thanour fictitious model at the beginning of this article would lead us to believe. We don’t know what percentage of people could be re-infected by Omicron. And we don’t know how Omicron affects children, who are an important re-infection vector.  

Further reading:

Early lab studies hint Omicron may be milder. But most scientists reserve judgmentScience, December 20th.

How severe are Omicron infections?, Nature, December 17th.

What It Takes to Understand a VariantNew York Times, December 14th.

Link to the original article: https://www.sciencepresse.qc.ca/actualite/detecteur-rumeurs/2021/12/21/sait-hospitalisations-causees-omicron-grand-chose

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This article is one of many under the heading Détecteur de rumeurs; click here for the others.

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