- Who is Omicron?
It is a new version of SARS-CoV-2 (the coronavirus at the origin of Covid) which was identified at the end of November in Botswana, then in South Africa.
Its peculiarity is its high number of mutations compared to the initial strain of the virus, known as Wuhan, and the previous variants, such as the Delta, which has largely dominated global contaminations since the summer of 2021.
It is not clear exactly where and how Omicron appeared.
A hypothesis seduced many scientists: the virus would have gradually mutated at low noise in the body of an immunocompromised person, a process that would have taken several months to produce a version markedly different from the initial strain.
Variants of the covonarivus John SAEKI AFP / Archives
- What is he changing?
It is obviously very contagious.
It was only a hypothesis when it first appeared, but it became a certainty in the first weeks of December, given the epidemic situation in several countries.
Omicron is spreading "at a rate that we have never seen with any other variant" and "is probably found in most countries," Tedros Adhanom Ghebreyesus, director-general of the World Health Organization (WHO ).
It has so far been identified in nearly 80 countries.
WHO Director-General Tedros Adhanom Ghebreyesus in November 2021 in Geneva Christopher Black World Health Organization / AFP / Archives
South Africa and its neighbors recorded an outbreak of Covid cases with the arrival of Omicron, which also saw a meteoric rise in several European countries.
This is the case of Denmark and the United Kingdom.
More broadly, Omicron could be dominant in Europe by mid-January, according to comments made this week by European Commission President Ursula von der Leyen.
Will he definitely replace Delta?
This is a high probability, but scientists are suggesting other possibilities: that Omicron supplants its predecessor for a time but ends up giving it back again or that the two variants coexist as is the case for certain strains of the virus. seasonal flu.
- What about vaccines?
This is one of the great challenges posed by Omicron, as current vaccines are already losing their effectiveness over time against Delta variant infections.
Mutations in Omicron are such as to considerably reduce antibody immunity against the virus.
Consequence: it can probably re-infect people previously infected with the virus and infect a large number of vaccinees.
Thus, according to a study from Imperial College London made public on Friday, the risk of being re-infected after having already had Covid is 5.4 times greater with Omicron than with Delta.
And several recent studies, done in the laboratory, show that the level of antibodies collapses against Omicron in vaccinated with Pfizer / BioNTech, Moderna, and, even more AstraZeneca or Sinovac.
A syringe of vaccine against Covid-19, December 15, 2021 in Sheffield, UK Oli SCARFF AFP
Admittedly, a booster dose seems to clearly boost immunity by antibodies, as announced by Pfizer and BioNTech in particular, but we are very far from knowing to what extent this effect persists over time.
However, this does not mean that vaccines lose all of their effectiveness.
Because antibodies are only one part of the immune response, which also involves cells called T lymphocytes. More difficult to measure, this "cellular immunity" nonetheless plays a very important role, especially against the forms severe disease.
In fact, a study published this week in South Africa suggests that the Pfizer / BioNTech vaccine remains rather effective against the severe forms generated by Omicron, including after the first two doses.
Omicron also seems to pose difficulties for synthetic antibody treatments, especially used in patients already hospitalized.
On the other hand, we can hope that it does not resist the anti-Covid pills recently announced by the Merck and Pfizer laboratories.
However, this is a hypothesis, linked to the functioning of these drugs, which still needs to be supported by the facts.
- Less dangerous ?
It is now the great unknown.
Clinical data from the past few weeks clearly suggests that Omicron is no more dangerous than its predecessors, including Delta.
It is "almost certain," eminent American scientist Anthony Fauci told AFP in early December, even believing that it could be less dangerous.
But should we bet on this eventuality?
It is a risky bet.
Already, a first death was recorded earlier this week in the United Kingdom.
Above all, scientists warn against an optical effect.
If Omicron is less dangerous but much more contagious, the consequences will indeed remain serious at the collective level.
"We are concerned that people consider Omicron to be benign," warned the head of the WHO.
"Even if Omicron causes less severe symptoms, the number of cases could once again overwhelm unprepared health systems."
© 2021 AFP