Variant BA.2 Omicron: “It explains the resumption of the epidemic in France”

[Mis à jour le 14 mars 2022 à 15h27] BA.2 is a subvariant of Omicronitself a variant of the Sars-Cov-2 coronavirus that appeared in France at the end of 2021.”What explains the resumption is the sub-variant of Omicron, BA.2, which is more contagious than its predecessor and which leads to this rise in the epidemic” said Professor Arnaud Fontanet on France Inter this Monday, March 14. A hypothesis confirmed by Jean-François Delfraissy, who estimated the same day on RTL than “this epidemic rebound was something expected, due to the extremely transmissible character of the BA.2 variant, which is 30% more transmissible than BA.1so we expected that there is this rebound, there now“.”The sub-lineage BA.2 is now the majority in France at 52% in week 9 (February 28-March 6) according to preliminary data and at 43% in week 8 (February 21-27)” indicates Public Health France in its epidemiological point of March 11. “The progress of BA.2 to the detriment of BA.1 is observed throughout the metropolitan territory, but at different levels depending on the region“added the organization. What is this new mutation? of Covid-19? Is it more contagious, more dangerous, than Omicron? the vaccine effective against this new variant? The symptoms are they different? 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“declared Jean-François Delfraissy, president of the Covid Scientific Council, at the microphone of France info Tuesday, January 25. Named BA.2, it is the youngest of the majority strain of this variant, called BA.1, which is the majority in Europe. The difference between BA.1 and BA.2 is significant, especially within the Spike protein. “The most recent data appear to confirm that BA.1 and BA.2 show similar severity and immune response evasion, and therefore BA.2 is not considered a distinct variant but is included in the Omicron VOC.” specifies Public Health France. A danish study published on January 20, 2022 and conducted by the research institute Statens Serum Institut (Copenhagen) pointed out that “the initial analysis does not show no difference in hospitalizations for BA.2 compared to BA.1″.

What is the rate of the BA.2 variant in France?

“The BA.2 sub-lineage is now majority in France at 52% in week 9 (February 28-March 6) according to preliminary data and at 43% in week 8 (February 21-27)” indicates Public Health France in its epidemiological point of March 11. “The progression of BA.2 to the detriment of BA.1 is observed throughout the metropolitan territory, but at different levels depending on the regionadded the organism. The BA.2 sub-lineage already reached 38% in week 6 (February 21-27). “The BA.2 sub-lineage continues to progress to reach 25% of cases in week 7 (from February 14 to 20) against 15.4% in week 6 (from February 7 to 13)” indicated Public Health France in its epidemiological update of March 3.

What are the symptoms of the BA.2 variant?

For the moment, there are no specific symptoms listed on the few cases of BA.2 sub-variants. 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 less severity (risk of hospitalization and admission to intensive care up to 80% lower )” reported Public Health France January 26.

Is the BA.2 variant more contagious than Omicron?

“The BA.2 variant is 30% more transmissible than BA.1“said Jean-François Delfraissy on March 14.”Early data from limited studies suggest that the BA.2 is 30% more transmissible than BA.1. In addition, an analysis of the data shows a growth rate advantage of BA.2 over BA.1 in the 43 countries with sufficient data on the sequences and the co-circulation of the two lineages.” had already indicated the WHO on February 16. “It seems that it is even more contagious (than the Omicron variant, editor’s note), that it presents significant risks of recontamination” declared Gabriel Attal during the Council of Ministers on February 2. The Danish study of January 31 reveals “an overall secondary attack rate of 39% in households infected with BA.2vs 29% in households infected with BA.1.”

Is it possible to be re-infected with BA.2 after Omicron?

A BA.2 infection can occur after a first BA.1 infection revealed the Danish study published on Tuesday 22 February. “Researchers studied the number of individuals who had two positive tests and used genome sequencing to look for the variants of the virus with which they had been infected.. The researchers found 67 cases in which the same individual had been infected twice with an interval of 20 to 60 days and where both infections were due to Omicron subtypes“. In 47 of the cases, the affected individual was first infected with BA.1 and then with BA.2. “The majority of those infected were young and unvaccinated, and most had mild symptoms during their infections“. If the original Omicron quickly spread, it is among other things because it can recontaminate people who already have antibodies.“, recalled epidemiologist Catherine Hill, interviewed by Le Figaro January 25. The duration of immunity may therefore depend on the variants, and especially on a new variant, which could circumvent the immunity acquired with infection with another variant. This was the case with Omicron at the end of 2021, which can partially escape protection from infection or the vaccine. And it seems that this is also the case with BA.2, even more contagious. On December 17, a Imperial College London study believed that “the risk of reinfection with the Omicron variant is 5.4 times greater than that of the Delta variant”.

Is the BA.2 variant more dangerous than Omicron?

“Omicron BA2 subvariant does not ’cause more severe form’ of Covid than BA1” according to Maria Van Kerkhove, technical officer of the WHO on the subject of Covid-19. She indicated that there was no not “difference in terms of severity between BA1 and BA2 and therefore a similar level of severity in terms of the risk of hospitalization“.”After adjusting for age, previous infections, gender, or ethnicity, Iand risk of hospitalization and severe form [du Covid-19] with BA.2 (0.87) would be even lower than with BA.1“according to a report published by the British Health Agency. The study focused on the risk of hospitalization defined as admission as an inpatient to the hospital or presentation to emergency care that resulted in admission, transfer or death, after BA.2 compared to BA.1. These results are still preliminary and based on a small number of cases, so “these estimates may change” afterwards. Preliminary analyzes in the UK showed a higher secondary attack rate for BA.2 compared to BA.1 (13.4% vs 10.3%) but a vaccine efficacy against similar symptomatic infections for the two sublineages. Further studies are underway to more accurately assess the transmissibility, severity, and immune response evasion of BA.2 compared to BA.1.” noted Public Health France.

“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. In a second time, 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 latest study from the British health agency.”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.”I‘vaccine efficacy is maintained against Omicron after administration of a booster dose, especially against severe forms“confirmed Public Health France on January 26.

Sources:

– “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.