Omicron Variant: What Scientists Already Know and Don’t Yet

Three weeks after the appearance of the Omicron variant, this newcomer continues to worry the planet. With his fifty transfers, he immediately aroused fear. A fear further reinforced by its impressive speed of diffusion in South Africa, from where it arose, and then by the great ease with which it has already managed to spread throughout the world. According to the latest data from the World Health Organization (WHO), it is in fact already present in 57 countries. If at the moment there are still many doubts, scientists are beginning to see its characteristics a little more clearly. The first clues have appeared in recent days. With good news and less good news, and also a lot of confusion, as often when awareness has not yet stabilized.

An impact on vaccines, the real scope of which has yet to be assessed

That’s the big question: is the Omicron variant capable of overcoming the barrier of immunity, either after an infection or a vaccine? Four first studies, conducted in South Africa, Germany, Sweden and by Pfizer-BioNtech suggest this, even if a booster dose would restore protection.

This in vitro work remains preliminary, not peer-reviewed, and related to very small numbers, but its results are consistent. “The South African study shows that there is a 40-fold decrease in post-vaccination neutralization with the Omicron variant, which is significant. On the other hand, this decrease is somewhat less marked in people who were vaccinated after an infection, which means that the efficacy of three doses of vaccines should probably remain high, “Professor Jean-Daniel Lelièvre, head of clinical immunology and infectious diseases, CHU, told L’Express. Henri-Mondor en Créteil (AP-HP) and expert in the Haute Autorité de Santé.

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The German study, published so far only on Twitter by one of its authors, found a similar reduction for the two vaccinated doses. For their part, Pfizer and BioNtech indicated in a press release that the serum (the part where the antibodies are located) from people vaccinated with two doses produced 25 times less antibodies against the Omicron variant than against the original virus “, indicating that two Vaccine doses may not be enough to protect against infection with Omicron. ” However, this decrease was not found with the serum of individuals who received their third dose. In the Swedish study, the decrease in efficacy with two doses appeared to be less.

Many more laboratory studies are expected to arrive in the next few days, probably with similar results. At the Institut Pasteur, Olivier Schwartz’s team plans to publish the pre-publication data next week: “We are studying the sensitivity of Omicron to antibodies produced after vaccination at one dose, two doses and three doses, for different types. of vaccines, and also after an infection ”, explains the researcher.

“Against Delta or against Omicron, it’s the same fight”

“But the decisive thing is to see what happens in real life, and in severe ways. With the Beta variant, there was a decrease in neutralizing activity, but the vaccine was still effective against the severe forms. However, it is too early. predict what will happen to the Omicron variant, because there is no strict correlation between what we see in vitro and in vivo, especially since other parts of immunity also come into play, such as cellular immunity ”, emphasizes Professor Lelièvre.

However, on this subject, Pfizer and BioNtech are already reassuring: “The vast majority of epitopes that attack vaccination-induced T cells are not affected by mutations present in Omicron, so vaccinated people could still be protected against serious forms “. However, the two firms also specify that this will have to be confirmed by monitoring in real life.

In this context, all the experts seem unanimous in stating that a third dose is more necessary than ever. “There will continue to be a way of efficacy of these vaccines, in particular for people who have received this immune booster. Therefore, ultimately, it is the same fight against Omicron and against Delta,” insisted Professor Jean-François Delfraissy, President of the Covid-19. Scientific Council, during its hearing on Wednesday before the senators.

The story probably won’t end there, however, sadly: “If the booster dose is likely to be protective against Omicron, the whole question will be how long this protection will last, as the amount of the antibody, even after the third dose, it will decrease over the months, “warns Olivier Schwartz. Perhaps then a fourth will be needed, as indicated by Professor Delfraissy, or even a new vaccine.” The laboratories are already working on it, but for now, it is too early to tell if necessary “, specifies Olivier Schwartz.

It’s probably not more serious, maybe even a little less

“So far, there is no evidence to suggest that this variant is more severe than the others. It appears comparable to what has been observed so far. Perhaps it results in a somewhat clinical form. Different with less respiratory damage and more global damage.” said Professor Jean-François Delfraissy.

Indeed, data from South Africa seem to show that the proportion of patients requiring oxygen is still lower than in previous waves. In Europe, none of those infected showed signs of severity, notes the European Center for the Prevention and Control of Infectious Diseases (ECDC). This gives some hope that Omicron is good news: a virus that is both benign and transmissible would quickly achieve herd immunity and end the crisis.

However, it still seems too early to bet everything on this hypothesis, for several reasons. In South Africa, the population is much younger than that of ancient Europe, so it is less likely to develop severe forms. If she is poorly vaccinated, she was probably largely immune to the violence of previous waves. Regarding the absence of death or serious forms linked to Omicron in Western countries, it is difficult to draw conclusions, given the small number of people affected at the moment.

Therefore, experts from the World Health Organization call for the utmost caution. “Even if this virus is not more virulent or more deadly, if we let it spread, it will cause as much as Delta or other variants a large number of cases, which will put pressure on health systems and more people will die.” warned Michael Ryan, head of emergencies for the World Health Organization during a press conference. In addition, recalled Tedros Adhanom Ghebreyesus, general director of the organization, “if the virus causes milder symptoms than Delta, we must not forget (…) that some of the infected people could suffer long or post-Covid symptoms of Covid, which we are only now beginning to understand. ”

A highly transmissible variant

A curve of the number of infections that flies almost vertically in South Africa. An impressive group in Norway, where a single person returning from Africa infected half of the 120 guests during a dinner. By the beginning of the week, almost 200 people had already been infected in Denmark, while the government had imposed confinement not only of contact cases, but also of the contacts of these contact cases. In the UK, the number of cases by Omicron appears to be doubling every two to three days – very strong growth, although the number of cases remains low for the time being (less than 600 on Wednesday), prompting the government to take new ones. restrictive measures, in particular with more teleworking and a vaccination passport in nightclubs.

Therefore, the evidence is mounting in favor of a very high transmissibility of Omicron. “It is probably a little higher than that of the Delta variant, which itself is very transmissible,” said Professor Delfraissy. But in what proportion exactly? Impossible to say at the moment, WHO experts stressed. In fact, Omicron emerged in South Africa at a time when there was not a wave of pollution. Therefore, it did not compete with other variants. “Now we must monitor how it is taking hold in other countries, where Delta circulates a lot, and if we have the same increase in the number of cases in different populations,” said the WHO, while specifying that their reproduction rate – the famous ” A “: should be known in the next few days.

If the trends seen in South Africa are confirmed in other regions of the world, however, we can expect Omicron to become the majority “in the coming months,” the European Center for Disease Prevention and Control said. But this forecast, which is based on very preliminary data, may still change.

“Transmission is linked to two factors: either contagion, the R, which is very high in the first calculations in South Africa and England, or a decreased sensitivity to natural or vaccine immunity. But high transmission is not Good news”. , underlined Pr Delfraissy.

Perhaps a tropism for children, I’m not sure at this point.

In recent days, South African doctors say they have seen a spike in child contamination, especially in the province where the Omicron variant circulates the most. However, it is too early to know if this virus has a particular tropism for children, or if they are more affected because they are not vaccinated and may have been less infected in previous waves. “The South African doctors confirmed to me this morning that they are seeing more hospitalized children, with somewhat strong symptoms, without for this reason having serious forms,” ​​said Professor Delfraissy. Here we will also have to wait to find out more.

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At this point, however, it seems that Omicron “is not the variant that changes everything and that will put us back in a dramatic situation”, in words used by Professor Jean-François Delfraissy, President of the Scientific Council, during his hearing before the senators. However, caution is still necessary, because its great transferability could still throw us into a difficult situation again in the coming months.



Christophe Donner.Christophe donner

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