Stealth Omicron BA.2, Found in 48 States, Should Remain Variant of Concern Says WHO

The Omicron BA.2 sub-variant should continue to be considered a variant of concern (VOC) and remain classed as part of the Omicron family of variants, the World Health Organisation (WHO) has said.

BA.2 has been the subject of interest and concern after it started spreading rapidly in some countries earlier this year, despite of the wider Omicron wave.

The sub-variant has become dominant in countries such as South Africa and Denmark and has been generally increasing as a proportion of sequenced viruses globally, relative to the BA.1 Omicron sub-variant that has accounted for the majority of Omicron cases.

As of February 22, the variant tracking website Outbreak.Info, which uses data from the virus genome reporting tool GISAID, showed that BA.2 had been detected in at least 80 countries worldwide and 48 U.S. states, including Washington, D.C.

In addition, modelling data from the U.S. Centers for Disease Control and Prevention (CDC) suggests BA.2 could have accounted for around 3.8 percent of sequenced cases in the U.S. between the dates of February 13 and February 19, with Omicron as a whole accounting for, essentially, all of the remaining 96.2 percent.

Data suggests that BA.2 is more transmissible than the BA.1 Omicron sub-variant that has accounted for the majority of Omicron cases. Data is less clear regarding its other characteristics.

This week, it was reported that there have been dozens of cases of people in Denmark catching BA.2 after having already caught BA.1 just weeks prior.

While Danish researchers said this was evidence of BA.2's reinfection capability, the cases remained rare and other limited data suggests that infection from BA.1 provides strong protection against BA.2, the WHO stated on Tuesday.

In addition, a study from Japan made headlines last week after researchers found BA.2 may cause more severe disease in hamsters compared to BA.1. The researchers said that based on their research, BA.2 should be given a Greek name and be classified as a unique variant of concern.

However, scientists noted that animal models are not always useful in predicting human outcomes and the WHO has noted that real-world data from South Africa, the U.K., and Denmark has shown no reported difference in severity between BA.2 and BA.1.

In a statement on Tuesday following a meeting by the WHO's Technical Advisory Group on SARS-CoV-2 Virus Evolution (TAG-VE), the WHO wrote: "Based on available data of transmission, severity, reinfection, diagnostics, therapeutics and impacts of vaccines, the group reinforced that the BA.2 sublineage should continue to be considered a variant of concern and that it should remain classified as Omicron.

"The group emphasized that BA.2 should continue to be monitored as a distinct sublineage of Omicron by public health authorities."

COVID test center
A health worker carries out a COVID test at a drive-through center in Nootdorp, Netherlands, on January 25th, 2022. The Omicron BA.2 sub-type has been closely studied by researchers recently. Patrick van Katwijk/Getty