What do we know about hospitalization caused by Omicron?


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This text was updated on December 29th

From the start, this is a seemingly simple mathematical calculation: in a dummy scenario where an omicron is three times more infectious than a delta but three times less, the number of hospitalizations would remain stable. If Omicron on the other hand is half severe, or of the same intensity, then hospitalizations will begin to increase very quickly, after two or three weeks of the increase in cases. However, at the moment we have little pathological data to learn.

1) in South AfricaThe first relatively good news came on the 14th of December. according to a report Published by insurer Discovery Health (the research has not been reviewed by other experts), double vaccination appears to provide weak protection against Omicron infection (33%), but relatively strong protection against hospitalization – 70%. From this study comes the 70% figure that we’ve seen pop up for a few days in several reports. It was also used, in Quebec, by INES to make, December 15, its forecast for the increase in hospitalizations during the holidays: a worrying increase, but it will remain within the capacity of hospitals.

Meanwhile, reports from South African hospitals indicated that the country It doesn’t look like he’s facingThe first half of December saw an alarming increase in the number of hospitalizations despite the skyrocketing number of coronavirus cases. study Previously published on December 21 (covering cases detected through December 6) tends to confirm this: it concludes that people with Omicron have a lower chance of ending up in hospital than those with other variants over the same period.

The downside: As we have noted several times since the end of November, the population of South Africa is smaller than that of Europe or North America. For example, the average age of the population studied by Discovery Health was 34 years old.

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finally, 1 week ago December 13The curve of daily cases in Gauteng province – where the crisis began – appears to be declining again. when ignored Whether this should be taken as an indication that the “Omicron wave” might have a short life, or that it would have started there much earlier undetected. That is why experts are closely watching the first European countries affected by Omicron.

2) in DenmarkThe first hospitalization data, released on December 13, brought mixed news. Although experts have suggested that the hospitalization rate for people with omicrons may be similar to the hospitalization rate for people with the earlier variants, the numbers have remained somewhat reassuring since then. As of December 20, there has been talk of nearly 22,000 cases of Omicron identified since November 22, including 13,000 cases since December 14, and 40 hospitalizations. With an important downside here, too: There may be a two-week delay between the rising curve of cases and the rising hospitalization curve.

On December 23, chief epidemiologist Tyra Grove-Kraus said he was confident Avoid the worst case scenario. Daily hospitalizations (about 125) were minimal than expected. Probably with the help of the third dose: already 37% of the population received it on Thursday.

3) In Great BritainAnd study From Imperial College London published on December 16, which was a model of laboratory analyzes, I came to two conclusions: on the one hand, that the protection offered by Pfizer’s double vaccination was poor to prevent infection and that a booster dose would likely be necessary; But on the other hand, the protection offered against serious injuries – those likely to lead to hospitalization – although reduced, is still high (80% vs. 95% against delta).

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However, this appears to have been confirmed in preliminary report From the same college, published Dec. 22: By comparing Delta and Omicron cases, researchers concluded that patients with Omicron would have a 15-20% lower risk of going to hospital, and 40% lower risk of staying in hospital for more than one night.

and one Another preliminary study From Scotland it goes in the same direction: By comparing delta and omicron cases detected from November 1 to December 19, researchers at the University of Edinburgh concluded that patients with omicron would have a 60% lower risk of hospitalization. This latest study, unlike the one from London College, looked only at hospital admissions, and excluded patients who had severe symptoms but chose not to go to hospital.

4) In the United States, On Christmas Eve, doctors began to be cautiously optimistic. In New York for example, Comment on Twitter Farzad Mashari from the Metropolitan Department of Health, if Omicron causes the same percentage of hospitalizations as Delta, then the hospitalization curve should start to rise, considering the number of days since the start of the increase in cases. December 13.

5) during face.. accomplish Held around the 15th of December by the World Health Organization, many of the international experts present reported preliminary lab data to confirm that the antibodies reacted less with Omicron than other variants – this is what makes vaccines susceptible to infection. But on the other hand, other mechanism In our immune system, T cells, keep replying wellProtecting infected people from more severe forms of COVID, thus reducing the risk of hospitalization.

An international team was previously published on December 14 Similar conclusions on the efficacy of six vaccines – including China’s Sinopharm and Russia’s Sputnik – against Omicron.

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Other studies, on humans or on mice, Owns I continue To appear during the holidays, tend to confirmed That our T cells will resist the omicron very well, preventing the majority of infections from becoming too severe.

in a A new South African study Published previously on 29 December, we note that the intensity of hospitalization in Gauteng province during the first 4 weeks of the Omicron wave, was lower than during the delta and beta waves: 28% of patients had severe symptoms, versus 60% and 66%.

Researchers who, all over the world, are trying to make models – that is, predict how the situation will develop – however, be careful: even a low hospitalization rate can translate into a lot of hospitalization, due to the speed with which Omicron spreads.

As much in Denmark as in Great Britain and Scotland, researchers also seem to agree on the fact that a third dose (a “booster”) increases protection dramatically. But Omicron has plenty of time to spread before a large percentage of the population gets a third dose, with the exception of possibly the elderly and most susceptible to infection.

This text was updated on December 22 by the South African study published on December 21, and the British and Scottish reports published on December 22. Updated Dec 22nd with the penultimate paragraph about modeling.
This text was updated on December 24 with the final paragraph on Denmark and preliminary data from New York.
Updated Dec 29th with the new South African T-Cell Resistance Studies and Hospitalization Study. The title has been lightened by deleting the phrase “not much”.

Photo: Our World in Data, December 21

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