Omicron: Institut Pasteur’s different scenarios about the variant

Published by Caroline J. · Photos by My B. · Published on 3 January 2022 at 16h15
As Omicron is hitting France at a swift pace, the Institut Pasteur released new modeling, unveiling the different and likely scenarios on the impact of Omicron in France.

While 208,000 new cases have been reported in 24 hours in France as of December 29, 2021, many people fear the days and weeks to come. This Wednesday, Olivier Véran did not hide his worries about the spread of the Omicron variant in the country, even speaking of a “tidal-wave”.

So, how will the epidemic evolve in France? How far will contaminations rise? What about hospitalizations? Shall one fear another overload? At this stage, it is hard to say, because of the many uncertainties about the Omicron variant, spotted for the first time in South-Africa. But this December 29, the Institut Pasteur issued their latest modeling involving the impact of the Omicron variant on the Covid-19 epidemic and its role in mainland France in the winter 2021-2022.

The Institut Pasteur shines a light on the different and likely scenarios about the effect of Omicron in the country, based on varied levels of seriousness and transmissibility of the new variant, while using a “mathematics modeling”.

Omicron’s impact on hospitalizations

Among the first hypotheses, the most likely here, the severity of the Omicron variant is cut down by circa 80% compared to Delta’s, but moderately more contagious than the latter. In this case, the hospitalization toll could peak at 2,700 per day, “without adjusting of behaviors”. And if the French limit their contacts down to 10% to 20%, then the hospitalization toll could peak respectively at 1,900 (-28%) and 1,400 (-48%).

But, in the event the Omicron variant shows a “high transmission asset”, then the hospitalization toll could peak at 2,700 per day, but cutting contacts down 20%, and 4,400 without limiting contacts. In the event of a “low transmission asset”, then the peak would not exceed 1,700 hospitalization per day.

Another likely scenario shared by the Institut Pasteur? The one where “Omicron’s seriousness is similar to the historic strain” (-54% compared to the Delta variant). In this case, the epidemic could “remain manageable” according to scientists, yet including “intermediary intensive measure in scenarios”. For instance, with high transmissibility, then hospitalizations could peak at 5,000 per day.

Contaminations and vaccination campaign

As for the new daily contamination toll, it could involve “hundreds of thousands of French” in January 2022, the Institut Pasteur warns. Yet, it could be only about mild symptoms “in most cases”.

Another Omicron impact pointed out by searchers? The functioning of the society could be “disturbed” because of “absenteeism caused by the infection wave”; a concern already raised by the Scientific Committee.

Last but not least, the Institut Pasteur delivers a few recommendations as for the vaccination campaign. Therefore, “the acceleration in giving boosters (1.2 million per day instead of the daily 800,000) could reduce the size of the hospitalization peak by 9-17%”, scientists explain in the document. “Vaccinating 90% of adults non-vaccinated, at a pace of 100,000 doses given per day”, could lower the hospitalization peak from 17 to 35%.

Careful though, as explained by the Institut Pasteur, “these scenarios are based on incomplete data and uncertain hypotheses. The spread of the SARS-CoV-2 virus is hard to anticipate and the dynamic of the epidemic could quickly change. Trajectories described depend on the hypotheses made; if the hypotheses do not occur, the dynamic observed could be different from projections”.

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