The certainties and the two great uncertainties that surround omicron

What impact will it have omicron in hospital services, and this could be the last wave of the COVID-19? They are the two main questions around the variant, much more contagious but less virulent than the previous ones.

What do we know about omicron?

Six weeks after its identification in South Africa, data from several countries coincide on two points: omicron is transmitted much faster than the previously dominant delta variant, and appears globally less severe.

Ómicron is progressing brilliantly in many countries and cases double every two or three days, something never seen before.

At the same time, data from “the United Kingdom, Canada, the United States and Israel suggest a reduced risk of hospitalization compared to the other variants (from 56% to 81%),” the Santé Publique France agency highlighted on Friday.

Early studies in South Africa indicated this trend. But these data are still incomplete and must be handled with prudence.

This raises an important question: it is not known if the fact that it is less virulent is due to the mutations of the variant or the fact that it infects people who were already partially immunized (thanks to the vaccine or from a previous infection). .

One element in particular could partly explain why omicron is both more contagious and less severe.

According to several studies, it seems to particularly infect the upper airways (nose, throat) but less the lungs, where COVID-19 becomes a serious pathology.

This particularity allows it to be expelled more easily, but at the same time, the virus is also more contagious.

Some specialists therefore recommend FFP2 masks, which protect more than surgical ones.

What consequences in hospitals?

For now, it is the great enigma.

The equation depends on two unknowns: Will omicron’s lower gravity compensate for the fact that it is much more contagious?

“Although the proportion of serious cases is lower, the fact of having a record number of cases can lead to a record number of hospitalizations,” American virologist Angela Rasmussen explained on Twitter on Friday.

The consequences for hospitals appear to be different from previous waves.

The omicron seems to saturate resuscitation services less, since it causes less serious forms. This is indicated, for example, by a recent report by the Danish Health Agency, SSI.

In December the number of new cases increased by 69% in Denmark, but hospitalizations only by 47%, while serious cases by 20%.

However, it is difficult to distinguish people hospitalized due to COVID-19 from those who suffer other types of ailments and who test positive upon arrival at the health center.

What about vaccines?

Omicron mutations appear to reduce the immunity of antibodies against the virus, so it can spread among many of the vaccinated people (and even re-infect some).

Several studies carried out in the laboratory show that the rate of antibodies falls against omicron among people who received the vaccines from Pfizer-BioNTech, Moderna and, even more so with AstraZeneca or Sinovac (Chinese vaccine used by about fifty countries).

A booster dose seems to clearly improve antibody immunity. At least that’s what different labs announced: Pfizer-BioNTech, Moderna and AstraZeneca. But one crucial piece of information is missing: it is unknown how long this effect lasts.

This does not mean that vaccines are not effective, because antibodies are only one of the tools of the immune response, which also relies on cells called T lymphocytes.

Although more difficult to measure, this “cellular immunity” is no less important, especially in severe cases of the disease.

Thus, a study presented in mid-December in South Africa suggests that Pfizer-BioNTech continues to be effective against severe forms caused by omicron, even before the booster dose (and certainly long after).

The last wave?

“Perhaps it is the last variant, perhaps the last wave”, ventured the French Minister of Health, Olivier Veran.

One of the heads of the Danish agency, Tyra Grove Krause, also expressed her “prudent optimism about the situation once we have overcome the omicron wave.”

But “the more omicron spreads, the more it is transmitted and more replicated, and the more susceptible it is to creating a new variant,” warned a WHO official, Catherine Smallwood, in a statement Tuesday.