A novel SARS-CoV-2 variant, the delta plus variant, has been identified in over 10 countries. Health authorities are raising concerns that the variant may have an increased ability to transmit, but they also note that this variant’s transmissibility is likely similar to that of the preexisting delta variant.

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Why has the delta plus variant of SARS-CoV-2 caused some concerns, and what do we know about it so far?
Image credit: DIPTENDU DUTTA/AFP via Getty Images

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As ever more SARS-CoV-2 variants emerge, governments and public health experts continue to consider the best strategies to contain their spread. There are currently 11 variants of the SARS-CoV-2 virus that the World Health Organization (WHO) is monitoring.

One of these variants, the delta variant — also known as the B.1.617.2 lineage — was first identified in India in December 2020 and quickly became the most common variant in the country.

It has demonstrated 40–60% increased transmission, in comparison with the previously dominant alpha variant, and is currently the dominant SARS-CoV-2 variant in the United Kingdom.

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Meanwhile, researchers recently identified another variant — the delta plus variant, also known as B.1.617.2.1 or AY.1.

The U.K. governmental agency Public Health England first declared it a “variant of concern” in a June 11 briefing, and on June 22, Indian authorities followed suit.

Since then, 11 countries have reported a collective 197 cases of COVID-19 caused by the delta plus variant of SARS-COV-2.

The delta plus variant is a sublineage of the delta variant, with the only known difference being an additional mutation, K417N, in the virus’ spike protein, the protein that allows it to infect healthy cells.

This mutation is also found in the beta and gamma variants, which researchers first identified in South Africa and Brazil, respectively.

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The WHO shared with Reuters that “For the moment, this variant does not seem to be common, currently accounting for only a small fraction of the delta sequences.”

Yet, “Delta and other circulating variants of concern remain a higher public health risk, as they have demonstrated increases in transmission,” the WHO added.

Furthermore, since India has labeled this variant a “variant of concern,” the country’s SARS-CoV-2 Consortium on Genomics (INSACOG), which is made up of 28 laboratories dedicated to whole genome sequencing of the SARS-CoV-2 virus and its evolving variants, continues to follow the evolution of delta plus.

INSACOG lists the following concerns regarding the delta plus variant:

  • increased transmissibility
  • stronger binding to receptors of lung cells
  • potential reduction in monoclonal antibody response

The spike protein is responsible for binding to a cell’s surface receptors, allowing the virus to enter. A mutation in the protein may strengthen this interaction, which could increase transmissibility, as per these first two points.

This mutation, however, is present in other variants, as well, so it is likely not a new source of concern.

Additionally, virologist Dr. Jeremy Kamil, from the Louisiana State University Health Sciences Center, suggested to the BBC that “Delta plus might have a slight advantage at infecting and spreading between people who were previously infected earlier during the pandemic or who have weak or incomplete vaccine immunity.”

But he also noted that this is not much different from the delta variant.

Other experts have also raised the third point, about the variant’s potential to reduce the effectiveness of monoclonal antibody treatments.

These include therapies such as the bamlanivimab and etesevimab and REGN-COV2 combination therapies, which researchers have shown to be beneficial in treating mild to moderate COVID-19 when given early during the course of the disease.

However, this reduced effectiveness “is not a major difference, as the therapy itself is investigational and few are eligible for this treatment,” said epidemiologist and vaccine expert Dr. Chandrakant Lahariya in a CNBC interview.

For the preexisting delta variant, many of the available COVID-19 vaccines show evidence of preventing hospitalization and severe disease.

The Pfizer and Oxford-AstraZeneca vaccines were highly effective, at respective 96% and 92% effectiveness after both doses. Studies on the Moderna and Covaxin vaccines also suggested they were able to neutralize this virus variant.

There are currently insufficient data on the vaccines’ effectiveness against the delta plus variant, but so far there have been no clear signs of the variant infecting people who have received vaccination. Furthermore, no countries with cases of the variant have reported spikes in infection rates.

The Indian Council of Medical Research has isolated the variant to test vaccine effectiveness and has stated that results will be ready in coming days.

While a new SARS-CoV-2 variant is inevitably concerning, there are no immediate indicators to suggest that delta plus is more infectious or dangerous than the other variants.

Further research and data from people with delta plus variant infections are needed to examine this variant’s characteristics and its ability to cause increased transmission or severity of COVID-19.

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