The WHO will continue to consider the BA.2 sublineage of Omicron as a variant of concern

World Health Organization (who) indicates that the BA.2 sublineage of Omicron It should continue to be considered a variant of concern and, for this reason, it maintains its study, observing that everything indicates that it is highly transmissible.

The WHO Technical Advisory Group on SARS-CoV-2 Virus Evolution (TAG-VE), meeting this Tuesday to discuss the latest evidence on the Omicron variant of interest, including its BA.1 and BA.2 sublineages, emphasized in that BA.2 should remain by public health authorities.

The Omicron variant of concern is currently the dominant variant circulating globally, accounting for almost all sequences reported to GISAID. Ómicron is made up of several sub-lineages, each overseen by the WHO and its partners. Of these, the most common are BA.1, BA.1.1 (or Nextstrain clade 21K) and BA.2 (or Nextstrain clade 21L).

Globally, the proportion of reported sequences designated as BA.2 has increased relative to BA.1 in recent weeks; However,

On the other hand, they note that BA.2 differs from BA.1 in its genetic sequence, including some amino acid differences in the spike protein and other proteins. Studies have shown that BA.2 has a growth advantage over BA.1. Studies are underway to understand the reasons for this growth advantage, but initial data suggest that BA.2 appears inherently more transmissible than BA.1, which currently remains the most common Omicron sublineage reported.

This difference in transmissibility appears to be much smaller than, for example, the difference between BA.1 and Delta. Furthermore, although BA.2 sequences are increasing in proportion to other Omicron sublineages (BA.1 and BA.1.1), it is still reported

Studies are evaluating the risk of reinfection with BA.2 compared to BA.1. Reinfection with BA.2 after infection with BA.1 has been documented; however, initial data from population-level reinfection studies suggest that infection is at least for the limited period for which data are available.

While reaching the above determination, the TAG-VE also analyzed preliminary laboratory data from Japan generated using animal models without immunity to SARS-CoV-2, which highlighted that BA.2 may cause more severe disease in hamsters compared to BA.1. They also considered real-world data on clinical severity from South Africa, the UK, and Denmark, where immunity from vaccination or natural infection is high: in these data, no difference in severity was reported between BA.2 and BA.1.