[Mise à jour le 3 juin 2022 à 10h43] BA.2 is a subvariant of Omicron, itself a variant of the Sars-CoV-2 coronavirus responsible for Covid-19 disease. It was defined at the beginning of April 2022 but circulates in France and Europe since end of 2021/beginning of 2022. It is in the majority in France and in the DROMs. “BA.2 (and its sub-lineages) is the majority in France, with 94% of the 837 interpretable sequences of the Flash investigation Week 20 (May 16-05)“, specifies Public Health France in its epidemiological point of June 2. Different recombinants between the BA.1 and BA.2 sublines have been detected in several countries (United Kingdom, Denmark, Finland, Germany, Israel). We count as follows: XE, XG, XH, XJ, XK, XL, XM, XN, XP, XQ, XR and XT. “A growing number of BA.2 sublines are defined to reflect the genetic diversification within this continuously circulating variant. Some of these BA.2 sub-lineages are particularly watched, because they carry a mutation that has been associated in Delta with increased transmissibility. BA.2.11, carrier of the mutation in question and circulating mainly in France, remains detected at very low levels and does not seem to have a competitive advantage over BA.2” adds the health organization. What is this mutation of Covid-19? the vaccine effective against this variant? What are the symptoms of BA.2 ? Update.
Definition: what is the new BA.2 variant?
“The BA.2 is a subvariant of Omicron. It is a “little cousin” of the Omicron variant“explained Jean-François Delfraissy, president of the Covid Scientific Council, at the microphone of Franceinfo in January 2022. Named BA.2, it is a sub-lineage of Omicron like BA.1 or BA.3. “The genetic sequence of the BA.2 subvariant differs from that of BA.1 and notably shows amino acid differences in the Spike protein and other proteins” the WHO said in February 2022.”The most recent data seem to confirm that BA.1 and BA.2 show similar severity and escape from the immune response, and BA.2 is therefore not considered a separate variant but as included in the VOC Omicron” specifies Public Health France. BA.2 “is the most contagious variant of the SARS-CoV-2 virus we have seen so far“, alerted Maria Van Kerkhove of the WHO, on March 19 at a press conference.
What is the rate of the BA.2 variant in France?
The BA.2 Omicron variant is more present than the BA.1 variant, which has been circulating mainly since the end of 2021 in France. As of June 2, according to Santé Publique France, BA.2 represents 94% analyzed Omicron sequences.
What are the symptoms of the BA.2 variant?
There are no specific symptoms identified in Covid cases contaminated with the BA.2 sub-variant. On the other hand for the Omicron variant “epidemiological investigations indicate a specific clinical presentation with more upper respiratory symptoms and less loss of taste and smell, as well as a lower severity (risk of hospitalization and admission to intensive care up to 80% lower)“reported Santé Publique France as of January 26, 2022. The symptoms of the BA.2 variant (like Omicron in general) can be:
- Tiredness ;
- Cough ;
- Fever ;
- muscle aches or body aches;
- Sore throat ;
- Runny nose ;
- Nausea and vomiting
- Unpleasant breathing (more rarely)
- Loss of taste and smell (more rarely)
Is the BA.2 variant more contagious than Omicron?
“BA.2 is more transmissible than BA.1 (Secondary attack rate of 39% for BA.2 against 29% for BA.1). A study also estimates that the generation interval (time between two cases) of BA.2 is 15% lower than that of BA.1. These differences in transmissibility explain the rprogressive placement of BA.1 by BA.2 observed globally” underlined Public Health France on March 25. BA.2 “is the most contagious variant of the SARS-CoV-2 virus we have seen so far“, informed Maria Van Kerkhove, epidemiologist at WHO, in March.
What are the risks of re-infection with BA2?
The frequency of possible reinfections with SARS-CoV-2 has increased markedly since the introduction and dissemination in France of the Omicron variant, at the beginning of December 2021, notes Public Health France. Even more so since the circulation of the BA2 sub-variant, which is more contagious than Omicron’s BA1.
Several recent studies have highlighted the possibility of occurrence of reinfection with BA.2 following infection with BA.1, including within a very short period of time (less than 60 days). “Nevertheless they agree on the fact that these are probably rare events.”
Is the BA.2 variant more dangerous than Omicron?
“If it has been shown that BA.2 was more transmissible than BA.1, the two sub-lineages are similar in immune response escape and severity“ indicates Public Health France on April 28. “Omicron’s BA2 subvariant does not cause a more severe form of Covid than BA1according to Maria Van Kerkhove, epidemiologist in charge of the emerging diseases unit at the WHO. However, with a large number of cases, you will see an increase in hospitalizations and this will turn into an increase in deaths..”
Which test to detect the BA.2 variant?
“In France, the screening strategy can detect all Omicron without distinction, whether they are BA.1 or BA.2 and therefore to know in a reactive way the level of circulation of the variant“indicates Public Health France. Secondly, a sequencing makes it possible to make the difference between the sub-variants, BA.1 and BA.2 “Screening makes it possible to reactively follow the Omicrons as a whole and sequencing allows a finer analysis of the different sub-lineages [BA.1 ou BA.2]“.
Are vaccines effective against the BA.2 variant?
“The efficacy of the vaccine against symptomatic disease caused by BA.1 and BA.2 is similar: after two doses the efficacy is 10% for BA.1 and 18% for BA.2, after three doses the efficacy against symptomatic disease is 69% for BA.1 and 74% for BA.2 Efficacy drops to almost 50% two and a half months after the 3rd dose for BA.1 and BA.2“according to the study by the British health agency published on February 25.”This suggests that vaccination is at least as effective in preventing acquisition of BA.2 and may be more effective in preventing transmission of BA.2 than BA.1“, remarked the WHO.”L‘vaccine efficacy is maintained against Omicron after administration of a booster dose, especially against severe forms“confirmed Public Health France on January 26.
What treatments to prevent infection with the BA.2 variant?
Several treatments by monoclonal antibodies are available to prevent Covid-19 infection. “The effectiveness of monoclonal antibodies varies between BA.1 and BA.2, sotrovimab being slightly less effective against BA.2 while tixagevimab/cilgavimab (Evushield) is less effective against BA.1” indicates Public Health France on May 18. Researchers from the Institut Pasteur, CNRS, Vaccine Research Institute (VRI), in collaboration with the CHR of Orléans, the AP-HP, KU Leuven (Catholic University of Louvain ) and Paris Cité University studied theefficacy of two combinations of monoclonal antibodies therapies Ronapreve (combination of two antibodies developed by Roche/Regeneron) Where Evusheld (combination of two antibodies developed by Astra Zeneca) against the variant Omicron (BA.1 and BA.2) of the coronavirus. “We show that the antibodies and the corresponding sera are little or not active against BA.1, but are more active against BA.2. Compared to Delta, the neutralizing activity is more severely diminished against BA.1: it takes 344 times more antibodies to neutralize BA.1, and 9 times more to neutralize BA.2“, explains Timothée Bruel, first author of the study published on March 23 in Nature Medicine and researcher in the Virus and Immunity Unit at the Institut Pasteur (CNRS joint research unit). Four Omicron infections have been described among the 29 patients treated with antibodies (including one severe case). “This indicates that, in this case, the treatment does not fully protect against infection or severe forms“explains Thierry Prazuck, co-lead author of the study and head of the infectious diseases department at CHR d’Orléans.
– “Serum neutralization of SARS-CoV-2 Omicron BA.1 and BA.2 sublines in patients receiving monoclonal antibodies”, Nature Medicine, March 23, 2022
– “SARS-CoV-2 variants of concern and variants under investigation in England”, British Health Agency, 25 February 2022
– “Coronavirus: circulation of SARS-CoV-2 variants’, updated on February 25, 2022, Public Health France
-“BA.2 is more transmissible than BA.1 but vaccinated people are less likely to become infected and to transmit the infection”, January 31, Statens Serum Institut.
– COVID-19: epidemiological update of January 27, 2022, Public Health France
– “Risk analysis on emerging variants of SARS-CoV-2”, January 26, 2022, Public Health France.
-“Now a variant of Omicron, BA.2, accounts for nearly half of all Danish Omicron cases” January 20, 2022, Statens Serum Institut.
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