On November 25, South African scientists threw a cold on the approach of the end of the year holidays, announcing the discovery of a new variant of Sars-CoV-2 with disturbing mutations, quickly baptized Omicron. Its progress has been accompanied by great concern, which has notably led many countries to suspend their links with South Africa and other African states, which has not prevented this variant from being detected in dozens of countries, including France.
Omicron spreads, but he advances masked. If its mutations are known and localized, many questions still arise about what they will change in the Covid-19 epidemic. While the first results of studies are starting to be announced, franceinfo summarizes the state of knowledge.
Undoubtedly greater transmissibility
the “potential for very rapid spread” of this new variant is one of the reasons for concern that had been put forward upon the announcement of its discovery by South African scientists on November 25, due to the number of “extremely high” mutations observed. They then observed more than 10; they are finally more than 50. The evolution of the epidemic in South Africa also feeds fears: the Omicron variant had already become the most present in the population on December 1, and the increase in contamination is qualified “exponential” by the authorities.
“Preliminary data suggests a substantial advantage” of the new variant on the hitherto dominant Delta, the European Center for Disease Prevention and Control confirmed on 2 December. The agency’s mathematical models suggest he might be involved in “more than half of infections (…) din the European Union within the next few months “.
If the idea that this variant is more transmissible seems to gain consensus, from French Minister of Health Olivier Véran to White House adviser Anthony Fauci, we do not yet know how transmissible it is. On Twitter, a researcher from the London School of Hygiene & Tropical Medicine estimated, on December 3, that Omicron had been shown to be 2.4 times more contagious than Delta in the province of Gauteng (South Africa), where it was identified. But its results have not been peer reviewed or published in a journal. And the South African context does not necessarily lend itself to comparisons with France: the country had, for example, been very affected by the beta variant, which has never established itself in our regions.
Greater resistance to vaccines … but not total
The majority of mutations observed in this new variant are in the Spike protein, which allows it to attach to cells, and which is targeted by the antibodies. What gives rise to fear that the immune reaction, even stimulated by a vaccine, is no longer sufficient to fight against it.
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Finally, no need to wait until the weekend to have the neutralization results for Omicron! …
But the news is not very good … https://t.co/p215N2y1D5– Claude-Alexandre GUSTAVE (@C_A_Gustave) December 7, 2021
The first studies on this point are very partial, and are based on the laboratory observation of serum of vaccinated patients (a liquid drawn from their blood) when it is confronted with the new variant. “Omicron partially escapes immunity induced by Pfizer vaccine”, says theAfrica Health Research Institute (AHRI), based in South Africa, in a statement (in English) published Tuesday, December 7. But its results, which have not undergone independent review, are based on just a dozen cases. The AHRI also observes that immunity remains “considerable” in patients who have both “been vaccinated and previously infected” – on an even smaller sample.
Pfizer and BioNTech laboratories announced on Wednesday that the immune response linked to their vaccine was “significantly reduced” versus Omicron for patients who received two doses, but three doses offered “a high level of protection “, comparable to that of two doses compared to other variants. At the same time as this mixed report, the two companies have announced that they are working on a version of their vaccine adapted to the new variant, which must be “available by March”.
After these very partial results, many questions remain unanswered. “NOTAbove all, we need data in real life to find out what is really going on “, admitted to AFP Willem Hanekom, director general of the AHRI. Especially since antibodies are only one part of the immune response, which also involves cells called T lymphocytes, whose action is more difficult to measure. “There is a wide variation in the reduction in antibody efficacy ranging from 4 to 5 times less to 40 times less in these different studies.” These are limited to studying the effect on the antibodies only, so “that the immune system is much more complex”, specified, Wednesday, the scientific chief of the WHO, the doctor Soumya Swaminathan.
“It is premature to conclude that the reduction in the neutralizing activity of the antibodies will have the effect of significantly lowering the effectiveness of the vaccines.”
Dr Soumya SwaminathanAt a press conference
Decreased performance in the laboratory also does not say whether Omicron, beyond contaminating more, will cause more severe forms. “There is no reason to doubt” of the protection of vaccines against severe forms of Covid-19, thus affirmed the person in charge of the emergencies of the WHO, Michael Ryan, Tuesday.
Symptoms that seem, for the moment, less severe
As cases of the Omicron variant multiply across the world, no deaths have yet been associated with this new variant. The first reports from South Africa concerning the severity of symptoms in infected patients are rather reassuring. On November 28, the President of the South African Medical Association, Angélique Coetzee, reported having received around thirty carriers of the variant in her office without any having to be hospitalized. She was describing symptoms “light” and “unusual” : little fever but “a itchy throat” and an “extreme fatigue”. The Pretoria hospital was watching for its part (article in English) that, on December 2, its Covid service contained 70% of patients showing no respiratory symptoms, and hospitalized for reasons other than the virus.
“Omicron appears to have an increased rate of reinfection, but less severe symptoms”WHO Director General Tedros Adhanom Ghebreyesus observed on Wednesday. He is “almost certain” that Omicron does not cause more serious cases than Delta, said White House adviser Anthony Fauci the day before. “There are some signs that it may even be even less serious.” But this sentiment still needs to be confirmed by data. The American epidemiologist believes that the situation will be clearer in “two weeks at least”, because severe forms take time to develop. And recalls that the comparison of South Africa with the United States or Europe is complicated, because the South African population is younger and less at risk.
If the virus were indeed more contagious, but less lethal, would that be good news or bad? Opinions differ. “It would give a group immunity and would participate in attenuating the Sars-CoV-2 in a mild seasonal virus”, estimated the CNRS virologist Bruno Canard on Twitter December 1. Corn “if it starts to circulate a lot, we would have even more significant contaminations than with the current variant”, qualified Olivier Véran during the press conference of the government, Monday. “Prationally, we would end up having a lot of serious forms anyway. “