A new wave of summer Covid and its impact are still uncertain.
What new variations?
Identified in early April by researchers in Botswana and South Africa, these new Omicron subvariants likely in fact emerged between mid-December and early January.
Having become the majority in South Africa, then in Portugal, they provoked new waves of the epidemic there.
In South Africa, “where BA.4 and BA.5 were initially detected and where BA.4 is now the majority, the peak of the epidemic wave was past mid-May and its impact was very moderate. BA .5 is now the majority in Portugal, where the incidence is increasing but still remains at lower levels than the previous wave”, summarized Public Health France on Friday.
Now, the beginnings of a rebound of contaminations and an advance of new incarnations of Omicron appear elsewhere.
In Europe, BA.4 and BA.5 are rapidly gaining ground in France where they should end up supplanting BA.2, which has dominated since the start of the year, as well as in the United Kingdom and Germany. Among the identified sub-variants, BA.3 never became established.
In France, government spokeswoman Olivia Grégoire spoke of a “slight turnaround” for the Covid epidemic after the Council of Ministers on Wednesday, speaking of “vigilance” but “no worries” until then.
The latest weekly figures from Public Health France confirm the quivering of cases and the advance of new sub-variants.
The relaxation of sanitary measures also contributes to the resumption of the epidemic, point out several specialists.
Both subvariants appear to be spreading even faster than previous members of the Omicron lineage.
“BA.4 and BA.5 can spread as our immunity ages, and do so faster than BA.2 because they have a double advantage of contagiousness and immune escape. BA.4 and BA .5 therefore induce a wave sooner than BA.2 would have done”, explains to AFP Mircea T. Sofonea, lecturer in epidemiology at the University of Montpellier, in the south of France.
Summer, synonymous with more outdoor activities, will it be a brake on a possible epidemic resumption? “While summer can be counted on to have a lower incidence than winter, it cannot, on its own, prevent a wave of contamination from taking place, as the example of Delta has shown ( fourth wave) in July 2021″, tempers the epidemiologist.
So far, there is no signal of an increased severity of BA.4 or BA.5 compared to other Omicron lines, according to several scientists. But “it is still too early to measure it correctly”, nuance Mircea T. Sofonea.
The observations from South Africa and Portugal have, for the moment, tipped some observers for reasoned optimism about the increased risks of hospitalizations and deaths.
“The BA.4/5 wave in South Africa did not result in many hospitalizations and deaths due to high population immunity,” Tulio de Oliveira, a virologist at the University of Kwazulu-Natal in South Africa, whose team announced the discovery of Omicron in the fall of 2021. “Of course, we don’t know the long-term effects…”
In Portugal, where the population is more vaccinated but also older, hospitalizations have however risen almost to the level of the previous wave.
Unlike other countries, particularly in Europe, South Africa and Portugal had not previously suffered a wave carried by BA.2.
Having crossed a BA.2 wave “could confer better protection against BA.4 and BA.5”, “genetically closer” to him, judged Public Health France in May. But this remains to be confirmed.
Either way, the immune shield erodes over time.
“While the protection conferred by an Omicron infection or a third dose of vaccine remains significant after five months against a severe form, it is greatly reduced against any infection”, underlines the Montpellier epidemiologist.
For the most vulnerable, a fourth dose of vaccine is already recommended in several countries, without waiting for the fall.
If it is no longer compulsory, wearing a mask indoors in certain cases is also recommended by several scientists, as is ventilation.