BA.2, nicknamed “Omicron’s little brother”, made its first appearance in France a few weeks ago. Mentioned for the first time by Véran during a press conference on January 20, this new derivative of Covid-19 has been scrutinized by scientists.

• Where does BA.2 come from?

BA.2 was first identified in India and South Africa in late December 2021. It is a subvariant, believed to have emerged from a mutation of Omicron (officially known as BA .1). Omicron himself was born from a mutation of Delta. Other sublines have already been referenced, such as BA.3 or BB.2, but they have received less attention from epidemiologists due to the dramatic increase in cases of people having contracted BA.2.

BA.2 has over 20 mutations, about half of which are in the spike protein. It is the famous protein which interacts with human cells and which is the key to the entry of the virus into the body.

>> More than half of Europeans will be infected with Omicron in the next two months, according to WHO

• Is this sub-variant as dangerous as Omicron?

The World Health Organization (WHO), which had classified Omicron as a “variant of concern”, does not at this stage distinguish between it and its BA.2 sub-line. For his part, Véran said that “as far as we know at present, it more or less corresponds to the characteristics that we know about Omicron”. It’s not “a game changer” at this stage, added Véran to try to reassure.

BA.2 is being studied closely by the scientific community, but there are no precise data yet on its resistance to vaccines or on the severity of the Covid-19 cases it causes. Scientists are beginning to speak out on the subject, while remaining cautious.

Virologist Tom Peacock of Imperial College London tweeted that “early observations from India and Denmark suggest there is no dramatic difference in severity from BA.1. These data should become stronger (one way or another) in the coming weeks.”

Peacock added that “there will likely be minimal differences in vaccine efficacy against BA.1 and BA.2. Personally, I’m not sure BA.2 will have a substantial impact on the current wave of Omicron of the pandemic.

“Several countries are near or even beyond the peak of BA.1 waves. I would be very surprised if BA.2 caused a second wave at this point. Even with slightly higher transmissibility, this is absolutely no change Delta-Omicron and instead will likely be slower and more subtle,” he predicted.

For epidemiologist Antoine Flahault, director of the Institute of Global Health at the University of Geneva, infection surveillance should make it possible to test the resistance of BA.2, in particular if people infected with the classic Omicron are again contaminated by the subvariant. However, the means must be given to detect BA.2 contamination in the population, which seems tricky at this stage and which does not seem to go without saying.

• Why is BA.2 so difficult to plot?

BA.2 poses certain challenges to scientists, as it is not easy to follow. A variation in PCR test protocols and the fact that the type of kit varies from one laboratory to another makes it difficult to reliably identify BA.2, according to Florence Débarre, a biologist at the Institute of Ecology and environmental sciences in Paris, interviewed by Liberation. “In the UK, the way testing is done makes it impossible to distinguish between BA.2 and Delta,” says Débarre.

There is a more precise but less commonly used tool for tracking variants: virus genetic sequencing. This makes it possible to identify the exact presence of this sub-variant. But in France, for example, only some of the lab tests are randomly subjected to this more in-depth and expensive form of analysis. Sequencing also has the disadvantage of being slow, which makes it unsuitable for tracking a rapidly spreading variant.

• Where is BA.2 most dominant?

The subvariant has been detected in at least 43 countries on all continents. It is thought to have become the most common variant in a number of countries, including India, Denmark and Sweden. In Denmark, the number of daily Covid-19 cases has started to rise again, just when the Danes thought they had already peaked.

The UK Health Security Agency (UKHSA) identified more than 400 cases in Britain in the first 10 days of January.

“The Danish authorities have no explanation for this phenomenon, but it is being closely monitored,” said the French Public Health Agency, which follows the latest developments in Denmark. This “suggests that BA.2 is even more transmissible,” Débarre agreed. In Europe, BA.2 has also been sequenced in the UK, Germany, Belgium, Italy and France, while North America, Asia and Australia have also recorded cases.

• Is the BA.2 developing so quickly in France?

To date, the subvariant has been detected “at very low levels” in France, says the French Public Health Agency. “We have an international situation where the Omicron variant is circulating a lot, so it’s normal that we see sub-variants over time,” the agency said Jan. 21.

France thought it had peaked in mid-January. But new infections seem to be on the rise again, to everyone’s surprise. 425,183 French people tested positive for Covid-19 on January 20. Over the past seven days, the average number of daily cases was 337,192, up 9% from the previous week.

BA.2 risks reigniting the epidemic in France, said Flahault, interviewed by La Dépêche. “In the UK, the number of new cases of Covid-19 is halving every seven days […] It was expected that France would follow suit with a delay of two weeks: this is not the case. And this new variant could be the source of the very recent increase in contaminations that we are currently observing.

“It is essential that the epidemiological-clinical surveillance systems have the capacity to very quickly define the characteristics of the new variant”, warned the scientific council on January 20. These “must be anticipated and prepared for”.

Flahault said the watchword was vigilance, not panic, because “at the moment we feel (case BA.2) that the gravity is comparable to the” classic Omicron cases.

This article has been translated from the original in French.