It has imposed itself on the sly in France but it is now causing a sharp increase in new contaminations. The BA.5 sub-variant, a descendant of the Omicron family, is now the majority among the new contaminations recorded in France. More contagious, and benefiting from the effect of erosion of the immune protection conferred by the vaccine and previous infections, it caused the week of June 20 to 26 a 53% increase in the incidence rate, and is beginning to make increase hospitalizations.
Where does this sub-variant come from?
BA.5 is a sub-variant of the Omicron family, one of the evolutionary branches of Sars-CoV-2, like Alpha or Delta. But unlike these two previous strains, Omicron and its subvariants (named BA.1 through BA.5) dominated infections in the year 2022, and they now account for the vast majority of infections worldwide.
The BA.5 subvariant was identified in May by researchers in South Africa, a particularly advanced country in sequencing tests, which had also been the source of Omicron sequencing. Scientists believe that BA.5 could come from an evolution of BA.2, the lineage of Omicron which became the majority in France in March. BA.5 is accompanied by another sub-variant, which is close to it, namely BA.4. “While the BA.2 variant was as different from BA.1 as the Delta variant was from the Alpha variant, the evolutionary divergence between BA.4 and BA.5 is more limited,” epidemiologist Mircea T. Sofonea in an interview on the site The Conversation.
According to the latest bulletin from Public Health France, posted Thursday, June 30, BA.5 is now the majority in new contaminations in France. “During the June 13 Flash survey, the BA.5 sub-lineage of the Omicron variant became the majority, representing 59% of the interpretable sequences, replacing the BA.2 variant which only represented 21%. BA.4. was, meanwhile, found in 6% of the sequences”, details SPF.
Is it more contagious?
BA.5 actually seems to have an even greater ability to transmit itself than its predecessors. The work carried out by the team of Samuel Alizon, modeler and research director at the CNRS, showed that BA.5 had a growth advantage of almost 10% compared to BA.2. This increased ability to develop in a population can be explained by two ways, either the virus is intrinsically more contagious (for example by developing a better ability to “attach” to cells in order to replicate better), or it is able to more skillfully circumvent the body’s natural immune defenses or conferred by vaccination.
This second hypothesis is already verified. A study published on June 22, 2022 in The New England Journal of Medicine (NEJM), shows that BA.4 and BA.5 manage to bypass the immune defenses in a particularly remarkable way. According to this study, the level of neutralizing antibodies in vaccinated people was much lower for BA.5 than for BA.1 or BA.2. “These data show that subvariants BA.2.12.1 (an evolution of subvariant BA.2), BA.4 and BA.5 substantially escape neutralizing antibodies induced by both vaccination and infection. Moreover, the neutralizing antibody titers against the BA.4 or BA.5 subvariant and (to a lesser extent) against the BA.2.12.1 subvariant were lower than the titers against the BA.1 and BA.2, suggesting that the Omicron variant of Sars-CoV-2 continued to evolve with increasing neutralization escape,” the researchers conclude.
Does it lead to more serious cases?
At this time, BA.5 does not appear to cause more severe cases, leading substantially to an increased risk of hospitalization or death. While new cases continue to grow at high speed in France, the curve of new hospitalizations is also increasing, but at a much slower pace. Nearly 125,000 new cases were recorded Wednesday evening by Public Health France, or 57% more than a week earlier and at the highest level since the end of April. By comparison, hospitalizations are up 35% from last week. Hospitalization rates were particularly high among 80-89 year olds (35.4 per 100,000 inhabitants) and 90 and over (61.8 per 100,000), specifies Public Health France.
The protection conferred by the vaccine decreases over time, and “people who contracted an infection with Omicron BA.1 in December are less well protected than they were at the start of the year”, summed up Samuel Alizon. But protection against severe forms continues to be very strong: “The same goes for the immunity conferred by vaccines: even if it remains very robust against severe forms, it decreases a little against less severe infections” .
What are the symptoms ? Are they stronger?
At this time, it is difficult to say that this subvariant inherently causes stronger symptoms. Public Health France does note an increase in the frequency of certain signs, such as fevers or sore throats or more marked fatigue in patients currently infected, but without proof that this is intrinsically linked to the virus. This could be due to a decline in vaccine protection, or due to reinfections.
These symptoms can last on average one or two days longer than the previous symptoms observed in people infected several months ago, “The cases of BA.4 and BA.5 presented more frequently than the cases of BA.1 a discharge nasal, nausea / vomiting”, or even loss of taste and smell, underlined the agency in a document on June 15. In addition “the median duration of the signs was seven days, longer than for the BA.1 cases”.
Do people who have never had Covid have more marked symptoms?
This assertion has been raised by several patients, who say they have never tested positive since the start of the epidemic before being contaminated recently and attributing their particularly “robust” symptoms to this new sub-variant. For the moment, there is no scientific data to confirm that a primary infection with the BA.5 subvariant of Sars-CoV-2 would cause stronger signs.
To answer this question, it would be necessary to be able to include in a specific cohort people who have never encountered the virus before their BA.5 infection, to compare them to a cohort of patients who have already contracted Covid via a previous variant, and who would currently be BA.5 positive. “For the moment, we do not have the answer”, answers Bruno Canard, virologist at the CNRS and specialist in these viruses.
Could he ruin our summer?
The rise in Covid-19 cases can be seen all over Europe. “As countries across Europe have lifted the social measures that were in place, the virus will circulate at high levels during the summer,” warned Hans Kluge, the organization’s director for Europe on Thursday. of ONU. But for the moment, the various European countries are very reluctant to put restrictions in place. The same goes for the French government, which despite a very strong resumption of cases, does not seem to be heading towards a mandatory vaccine recall, a return of the health pass, or an obligation to wear a mask, in particular because the pressure on the hospital still seems measured.
The seventh wave of Covid-19 should therefore “not spoil the summer”, said Thursday the president of the scientific council Jean-François Delfraissy on RTL. But the healthcare system could be under pressure again towards the end of July. “Where is the difficulty for this summer is that we have a surge with the new variant (BA.5) – and we expect 1500 daily hospital admissions within a week – it that is to say, like in March, when the supply of care is weaker”, he noted. “It is enough for there to be a shift from a greater number of hospitalizations linked to Covid to a tired healthcare system and there will be a difficult balance at the end of July-beginning of August” at the time of the peak, he said. he warned.
To limit as much as possible the deaths linked to Covid and a new saturation of hospitals, the health authorities therefore insist on a vaccination booster for the most fragile, whose immune system and memory are less robust. “You have to get vaccinated now if you are over 60 and have a number of risk factors,” urged Jean-François Delfraissy on Thursday. “Because these vaccines exist, they are effective against the BA.5 variant on the occurrence of severe forms, and the new vaccines that will be available to us will have an availability that we do not yet know and that I rather estimate in October or early November,” he added.
Is there a suitable vaccine?
Vaccines suitable for this variant are not yet available. In the United States, a committee of American experts decided at the beginning of the week in favor of a vaccine recall specifically targeting Omicron, auguring a need for annual injections against Covid, like the flu. .
The two industry giants, Pfizer and Moderna, are currently developing a vaccine against Omicron. They recently announced that these vaccines show promising results. The experts however did not have to specify which sub-variant of Omicron they would like to see targeted: against BA.1, the first lineage of Omicron, or against BA.4 and BA.5. The American drug agency, the FDA, for its part told manufacturers on Thursday that the booster injections planned for this fall and winter should include elements specifically targeting the latter sub-variants.
The track that seems to be favored by scientists today is that of a vaccine that would target both the first strain of the virus, to obtain broad protection, and the latest BA.4 and BA.5 sub-variants.
Pfizer has published preliminary results showing that its vaccine against BA.4 and BA.5 caused strong antibody production in mice, but has not yet begun clinical trials in humans. Novavax, which makes a “subunit” vaccine (which contains part of the virus but not the whole virus), said it could come up with a cure for BA.4 and BA.5 by the end of the week. year.