After the “British” variant detected in the United Kingdom and which keeps the authorities in check as it is more contagious, comes the “South African” variant of the new coronavirus Sars-CoV-2, which causes COVID-19, which could be immune to vaccines.
These are the keys to the two new strains detected and that concern the international community:
What are the strains of the virus of concern?
All viruses constantly mutate. In fact, virus mutations are a key factor in the evolution of biodiversity. Mutations are changes that occur when viruses replicate.
Scientists have observed multiple mutations in Sars-CoV-2 since it first appeared, the vast majority of them inconsequential, but some may give you a survival advantage, including greater transmissibility.
Detected in November in the UK, the variant B.1.1.7, now called VOC 202012/01, “probably” originated in south-east England in September, according to Imperial College London.
It has spread rapidly throughout the UK and has now been detected in dozens of countries around the world, from the United States to South Korea, India, France and Denmark.
Most of these cases are linked to the United Kingdom, but in a few cases no link to the United Kingdom could be found, demonstrating that this variant has already taken hold at the local level. This is what is happening in Denmark, one of the countries with the largest sequence of samples, where 86 cases have been identified (with increasing frequency).
Another variant, called 501.V2, is now the majority in South Africa. It has been detected in samples dating back to October and has been identified in a few other countries around the world, including the UK and France.
In both variants, the cases are probably underestimated, according to experts.
These two variants have several mutations, one of which, called N501Y, is of particular concern to scientists. The mutation is found in the spike protein of the coronavirus, the “spike” on its surface that allows it to adhere to the ACE2 receptor on human cells to penetrate them and thus plays a key role in viral infection.
This mutation, called N501Y, is known to increase the virus’s ability to bind to the ACE2 receptor. The two variants, both the “South African” and the “British”, have presented this type of mutation.
“There is no clear relationship between ease of binding to ACE2 and increased transmissibility, but it is plausible that such a relationship exists,” says the European Center for Disease Prevention and Control (ECDC).
Several scientific studies, which have not yet been peer-reviewed and which are mainly based on modeling, conclude that the British variant is significantly more transmissible. This confirms initial assessments by the NERVTAG group of researchers advising the UK government, who estimated that transmission is increased by 50-70%.
Thus, according to calculations by the London School of Hygiene and Tropical Medicine (LSHTM), the British variant would be between 50 and 74% more contagious.
For their latest report, released Thursday, researchers from Imperial College London analyzed thousands of Sars CoV-2 virus genomes sequenced between October and December. Using two different methods, they concluded that this variant has a “significant advantage” in terms of contagion: 50 to 75% more contagious, or a virus reproduction rate (R) between 0.4 and 0.7 higher than that of the virus. usual virus.
Preliminary results for the South African variant also indicate higher transmissibility, but less data are available.
However, some experts believe there is not enough data to accurately assess the contagion of the two variants.
“We must be cautious. The result in terms of incidence is a combination of factors that combines the characteristics of the virus but also the established prevention and control measures” (distancing, use of masks, closure of public reception establishments …) Bruno Coignard, director of infectious diseases at the French public health agency Santé Publique France, told AFP.
“There is no information on the fact that infections by these strains are more serious,” the ECDC noted. But the risk “in terms of hospitalizations and deaths is high.”
“Higher transmissibility possibly means a much higher incidence, and therefore, even for the same fatality, greater pressure on the health system”, Bruno Coignard continues.
A Sars-CoV-2 variant “50% more transmissible would pose a much bigger problem than a 50% more lethal variant,” insists British epidemiologist Adam Kucharski on Twitter, with statistical evidence to back it up.
With a reproduction rate of 1.1, a mortality rate of 0.8%, and 10,000 infected people, we would end up with 129 deaths after a month, he explains. If the mortality rate is increased by 50%, the number of deaths would reach 193. But if the transmissibility rate increased by 50%, there would be 978 deaths.
The impact would be particularly significant in countries where even a small increase in transmissibility would push the reproduction rate above one, accelerating the epidemic.
The British variant is “really the concern of the moment” because “it can plunge us into an extremely complex situation,” epidemiologist Arnaud Fontanet, a member of the Scientific Council that guides the French government, warned on radio Franceinfo on Monday.
On the other hand, the first studies on the British variant also show a greater contamination of young people under 20 years of age, which raises the question of whether or not to open schools.
Thus, the LSHTM study considers that restrictive measures such as containment in the UK in November would not be effective enough to control the epidemic “unless schools, colleges and universities are also closed”.
Are vaccines still effective?
While the immunization campaigns that have just begun offer hope for a way out of this global health crisis, there are doubts about the ability of vaccines to combat the new variants.
For both variants, “there is not enough information available at this stage to estimate (whether they pose) a risk to the efficacy of the vaccine,” says the ECDC.
“Based on the current state of our knowledge, experts believe that current vaccines will be effective against these strains,” said Henry Walke of the US Centers for Disease Control and Prevention (CDC) at a conference on press on Wednesday.
However, the South African variant seems, at this stage, to raise more questions than the British.
A specific mutation present in this variant, and not in the British one, could theoretically “help it to evade the immunological protection conferred by a previous infection or by vaccination”, explained Professor François Balloux, from University College London, quoted by British Science Media Center on Monday.
Let us remember that the two most widespread vaccines, those of Pfizer / BioNTech and Moderna, are based precisely on the DNA sequence of the spike protein, which has mutated in these viariants.
However, at the moment there is no indication that this mutation is sufficient for the South African variant to be resistant to current vaccines, he said.
The German laboratory BioNTech, which, together with Pfizer, originally developed the world’s first licensed vaccine against Covid-19, has ensured that it is capable, if necessary, of delivering a new vaccine “in six weeks” to respond to a mutation .
How to fight it?
It is “illusory” to think that we can eradicate or totally prevent the spread of new variants, says Coignard, noting that the goal is to “delay as much as possible” their spread.
Thus, for countries where cases of new variants are not widespread, the CEPD recommends “efforts to curb the spread, similar to those made at the beginning of the epidemic”: testing people arriving from risk areas with possible quarantines, isolation and monitoring of reinforced contacts for infected people, limitation of travel, etc.
It also requires that the incidence of these variants be monitored, in particular by increasing the sequencing of viruses.
Some PCR tests can also give an indication of the presence of the British variant, and then better orient the sequences, explained Professor Fontanet, according to which “extremely aggressive surveillance” is essential.
At the individual level, “as these variants seem to spread more easily, we must be even more vigilant in our preventive measures to stop the spread of Covid-19,” insisted Dr. Walke, referring to the use of masks, physical distancing, hand washing and ventilation of closed spaces, not forgetting to avoid crowds.