What is Delta Plus AY.4.2? Should we be concerned about new highly mobile COVID-19 variant?

New Delhi, Oct 25: A new mutation of the Delta variant of COVID-19 which was being monitored and assessed in the UK has now been classed as a Variant Under Investigation (VUI) amid concerns of its increased growth rate, with experts warning it is a reminder that the pandemic is not over.

AY.4.2, dubbed "Delta Plus" and now named VUI-21OCT-01 by the UK Health Security Agency (UKHSA), has been under closer scrutiny in recent days after evidence indicated that it spread more quickly than the dominant Delta variant.

While evidence is still emerging, so far it does not appear the new VUI causes more severe disease or renders the vaccines currently deployed any less effective.

"The Delta variant sub-lineage known as Delta AY.4.2 was designated a Variant Under Investigation by the UK Health Security Agency on 20 October 2021 and has been given the official name VUI-21OCT-01," the UKHSA said.

India's Covid genomic surveillance project is on high alert after the detection of a sublineage of SARS CoV 2's delta variant in the UK and the USA.

What is AY.4.2?

AY.4.2 is the proposed name for a new Delta subtype. It's a combination of AY.4 plus the S:Y145H spike mutation. At present, this new subtype represents about 8-9% of cases in the UK, says Christina Pagel, PhD, director of the Clinical Operations Research Unit and professor of operational research at University College London.

"The designation was made on the basis that this sub-lineage has become increasingly common in the UK in recent months, and there is some early evidence that it may have an increased growth rate in the UK compared to Delta. More evidence is needed to know whether this is due to changes in the virus' behaviour or to epidemiological conditions," it said.

According to official statistics, the original Delta variant - first identified in India and later classed as Variant of Concern (VOC) in the UK - remains overwhelmingly dominant in the UK, making up approximately 99.8 per cent of all cases.

As of October 20, there were 15,120 cases of the new VUI-21OCT-01 confirmed by whole genome sequences in England since it was first detected in July.

In the last week, VUI-21OCT-01 accounted for approximately 6 per cent of all Delta cases -- confirmed through whole genome sequencing in all nine regions of England.

Meanwhile, In the US, the AY variants-aka Delta variants-are listed by the US Centers for Disease Control and Prevention (CDC) as variants of concern.

CDC is continuing to track lineages and sub-lineages of Delta and all other variants. Over the past nine months, as we have previously reported, we have ramped up our sequencing capabilities in partnership with local public health and academic institutions. We particularly monitor for sub-lineages that could impact therapeutics, such as monoclonal antibodies and vaccines.

At this time, there is no evidence that the sub-lineage AY 4.2 impacts the effectiveness of our current vaccines or therapeutics, and CDC will continue to follow up.