COVID: WHO to classify Omicron sub-variants separately due to dominance

The World Health Organisation (WHO) says it has updated its tracking system to separately evaluate new Omicron variants of COVID-19.

Omicron is the latest variant of the coronavirus that surfaced in 2021. Omicron (B.1.1.529) is referred to as a variant of concern (VOC) as it spreads very rapidly.

In a statement on Thursday, WHO said the tracking system would enable proper alignment with the existing global variant landscape.

The organisation said updating the tracker would also allow independent evaluation of the widespread Omicron sub-variants and enable proper examination of new variants.

“SARS-CoV-2 continues to evolve. Since the beginning of the COVID-19 pandemic, multiple Variants of Concern (VOCs) and Variants of Interest (VOIs) have been designated by WHO,” the statement reads.

“This is based on their assessed potential for expansion and replacement of prior variants, for causing new waves with increased circulation, and for the need for adjustments to public health actions.

“Based on comparisons of antigenic cross-reactivity using animal sera, replication studies in experimental models of the human respiratory tract, and evidence from clinical and epidemiological studies in humans.

“There is consensus among experts in WHO’s Technical Advisory Group on SARS-CoV-2 Virus Evolution (TAG-VE) that compared to previous variants, Omicron represents the most divergent VOC seen to date.’’

WHO raised concern over the rapid evolution of the Omicron viruses which affect the upper respiratory tract (versus lower respiratory tract) compared to the previous Omicron variants.

It said the “Omicron viruses account for more than 98 percent of the publicly available sequences since February 2022 and constitute the genetic background from which new SARS-CoV-2 variants will likely emerge”.

WHO said the previous classification of Omicron sub-lineages as part of Omicron VOC did not have the granularity required to correlate new descendant variants.

“Therefore, from March 15, the WHO variant tracking system will consider the classification of Omicron sublineages independently as variants under monitoring (VUMs), VOIs, or VOCs,” it added.

“WHO is also updating the working definitions for VOCs and VOIs.

“The main update consists in making the VOC definition more specific, to include major SARS-CoV-2 evolutionary steps that require major public health interventions.

“For the updated definitions, please visit the WHO variant tracking website.”

The organisation said new Greek labels will be given to VOCs, adding that it would stop assigning tags to variants of interest (VOI).