Covid-19: WHO continues to monitor ‘several descendent lineages’ of Omicron variant

The World Health Organisation has said that it is continuing to monitor “several descendent lineages” of the Omicron variant of the coronavirus, including two new sublineages that have additional mutations associated with potential “immune escape characteristics.” The Covid-19 Weekly Epidemiological Update, released by WHO on Tuesday, said that the Omicron variant remains the dominant one circulating globally.

WHO said it continues to monitor several descendent lineages under the Omicron Variant of Concern, including BA.1, BA.2, BA.3 as well as now BA.4 and BA.5. It also includes BA.1/BA.2 circulating recombinant forms, such as XE.

“A small number of sequences of BA.4 and BA.5 descendent lineages have now been detected in a few countries. Both have additional mutations in the Spike region (S:L452R, S:F486V) and unique mutations outside of Spike. The S:L452R and S:F486V mutations are associated with potential immune escape characteristics,” the global health organisation said.

It added that it is working with scientists to further assess the characteristics of these lineages and their public health implications. “WHO recommends countries to continue surveillance, where possible, and rapid data sharing on publicly available databases.”

According to WHO, the SARS-CoV-2 virus continues to evolve. With such intense transmission worldwide, further variants, including recombinants, will emerge. “This is expected.”

WHO is tracking the two new sublineages (BA.4 and BA.5) as part of the Omicron variant.

These variants have additional mutations that need to be further studied to understand their impact on immune escape potential. Only a few dozen sequences of these variants have been reported from a handful of countries.

WHO is working with scientists to better understand their current spread as well as any potential impact they may have.

WHO said that Omicron’s properties of immune escape have been associated with the rapid and almost synchronous increase in the global incidence of Covid-19 cases reported until the end of January 2022.

A further increase observed at the beginning of March was driven primarily by a delayed increase in case incidences in the Western Pacific Region and a rebound in the number of new cases reported in the European Region.

“This trend was likely due to a combination of factors, including the predominance of the Omicron Pango lineages BA.1, and then BA.2, with a transmission advantage over other Omicron lineages; relaxation of public health and social measures (PHSM); and waning of humoral immunity following vaccination and/or prior infection,” it said.

“The recent detection of emerging recombinants of the Delta-Omicron and Omicron descendent lineages requires ongoing close monitoring.”

“There is particular concern about reaching the most vulnerable populations who remain unvaccinated, particularly those of older age and those with comorbidities,” it said, adding that globally, an estimated 35 per cent of those aged 60 years and over are awaiting completion of the primary vaccination series.