11:15 p.m., March 19, 2022, amended to 11:36 p.m., March 19, 2022
Covid-19
came back with spring. Or rather, we realize that he was prowling, invisible and dangerous for the most fragile. Two years after the start of the pandemic, we wanted to believe that the threat could disappear as if by magic, because we couldn’t take it anymore, and that the ordeal of the Ukrainians taught us what a real “war” was. The eternal harbingers of a rebound are there, however: loved ones face the fever at the bottom of their beds; the daily number of new positive cases jumped (82,356 on average over seven days the day before yesterday), certain Regions experiencing a sharp increase in incidence (+ 40% in Hauts-de-France, + 34% in Brittany); and, even if hospital pressure continues to decline slightly, the number of new admissions to conventional care services is increasing in the north of the country.
A virus “in the process of domestication”
The example of the United Kingdom, where the “resurgence” of the epidemic – ahead of France – is fueled by the spread of the Omicron BA.2 sub-variant, calls for caution. There, concern is mounting, especially for the oldest people, who are now also infected. Scotland, a region in which all restrictions have not been lifted as in England, is recording a record level of incidence.
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Omicron has been generating a monstrous wave since the beginning of January, the real size of which is unknown
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Our astonishment at the resumption of the epidemic has the gift of making the experts smile. « The virus is being domesticated but it can only be gradual, philosopher the Swiss infectiologist and epidemiologist Didier Pittet. And, like the other four families of coronaviruses of the past, responsible for winter colds, which unfortunately had little interest in us until the appearance of Sars-CoV-2, it is with us forever. »
In the eyes of specialists, there are three main causes of this endless fifth wave. First, the replacement of the Omicron BA.1 sub-variant with BA.2, another sibling quite similar but about 30% more transmissible. « Omicron, a terribly contagious virus which generally causes few symptoms, has been causing a monstrous wave since early January, the actual size of which is unknown., analyzes Professor Pittet. Even in France where we still test a lot, there are probably five to ten times more people infected than screened. »
A decline in protection also against severe forms
Second reason for this rebound: the multiplication of social contacts, from morning kisses to dinners with friends. The phenomenon having started well before the lifting of the obligation to wear a mask in closed places and the vaccination pass on March 14. « The human factor has a great influence on the level of circulation of the virus, we have resumed a normal life and very few of us keep the mask in closed places. », observes Anne-Claude Crémieux, professor of infectiology and member of the Academy of Medicine.
Third, the decline, over time, of the immune protection conferred by vaccination. « The bad news of 2021 has been the rapid decline in the effectiveness of vaccines in preventing infections, decodes Professor Crémieux. But what worries us the most is the decline in protection against severe forms, starting four months after the booster. » It is for this reason that the executive is offering a fourth dose to people over 80 and that epidemic watchdogs are advising people over 60 and frail people to keep the mask on and avoid risk situations.
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The human factor has a great influence on the level of circulation of the virus
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On the other hand, no expert can say what the next few weeks will look like. Are we going to face a moderate wave or a small wave? Like the scientific council to which he belongs, virologist Bruno Lina estimates, on the basis of the most recent models from the Institut Pasteur team, that the peak could exceed 100,000 contaminations. But be careful, we are entering a gray area. « It is difficult to anticipate the evolution of each of these three factors, says Anne-Claude Crémieux. The important thing is to remain very reactive. »
The advantage of a “natural recall”
While being aware of the limits of modeling because they do not take into account the climate, a fourth determining factor but impossible to put into equation. « We can’t say if the sunny days will decapitate Omicron or not », adds Didier Pittet, who points out that this highly contagious variant responsible for infections that often go unnoticed complicates the work of modellers.
The Swiss epidemiologist nevertheless gives us a reason for hope: « We must imagine immunity as successive layers of paint. Thanks to regular doses of vaccine, the majority of us are now protected against severe infections and even death. The good news with Omicron is that a trivial infection with this less aggressive variant generates a different type of immunity than vaccine immunity. This form of immunity could protect us against future infections, much like the nasal vaccine we’re all hoping for. » Although the assumption of such “natural reminder” is not yet certain, we begin to dream that Omicron the-not-so-bad guy stays with us for a long time. Because only the arrival of a more dangerous variant could really spoil the spring.