The story so far: Scientists around the world and in India are concerned about ‘Delta plus’, an emerging form of the Delta variant of the novel coronavirus , which allows it to “escape” antibodies in recently approved treatment regimes.
What is the Delta plus variant?
Formally known as AY.1 or B.1.617.2.1 , it’s a variant of Delta (B.1.617.2), which was first identified in India. It has an additional mutation called K417N, which has previously been identified in the Beta variant (first found in South Africa) and the Gamma variant (first detected in Brazil). These variants are characterised as being highly infectious and may reduce the potency of vaccines.
Five Indian labs submitted data on this modified variant in May and June to the Global Initiative on Sharing All Influenza Data (GISAID). Seven of the around 28,000 coronavirus genomes sequenced out of India so far reportedly belong to the AY.1 lineage. Globally, 143 genomes have been labelled as AY.1 so far and reported from Nepal, Portugal, Switzerland, Poland, Japan, Russia, Turkey, United Kingdom, France, United States and Canada, besides India. At 45, the U.K. has reported the maximum number of instances, followed by Switzerland (23), and Portugal (21). The number of cases reported from a country is not always indicative of the prevalence of the variant and has to do with the extent of genome sequencing of virus samples. The U.K. has sequenced nearly 466,437 samples and reported 45 cases, the U.S. has sequenced 549,164 samples and reported 12 cases, whereas the number of samples India has sequenced is only about 5% (28,065) of these figures.
Why is it an area of concern?
The Delta variant is now regarded as the most prevalent one in India, comprising nearly 31% of the 21,000 community samples processed until late May. This variant has significant differences compared to the strain that has been used by pharma companies to design vaccines, and tests are needed to check if the existing vaccines continue to be effective against the variants dominant now. Tests in the U.K., South Africa, and Brazil have shown that vaccines, while effective, appear to produce fewer antibodies when confronted with variants such as Delta. The concern is that because the Delta variant has a cavalcade of mutations that have allowed it to dominate in several countries, including India, another form may pose new challenges to the management of the pandemic in India.
The ICMR-National Institute of Virology and the CSIR-Centre for Cellular and Molecular Biology, Hyderabad have conducted laboratory tests to determine the potency of Covishield and Covaxin against the Delta variant. While antibodies continued to be produced against the variant, they were fewer than those produced against the strain used by companies to prepare their vaccines. However, antibody levels are not the only markers of immunity. There is little evidence so far specifically linking AY.1 to large outbreaks and significant disease transmission, which is why it has not yet appeared in the World Health Organization’s list of ‘Variants of Concern’ , which includes Alpha, Beta, Delta, and Gamma variants. Early reports say AY.1 is diverging into two sub-lineages — one cluster has been found in California, and a larger cluster comprises sequences from eight other countries including Nepal, India and the U.K.
Can existing drugs help?
An additional concern with the AY.1 is the presence of the K417N mutation. According to a database of the CSIR-Institute of Genomics and Integrative Biology (CSIR-IGIB) , the mutation was associated with resistance to a newly developed monoclonal antibody treatment drug, Casirivimab and Imdevimab, for those with moderate and severe disease but at high risk.
Marketed by Roche and Cipla in India, the drug was recently approved by India’s Central Drugs Standard Control Organisation . The price for each patient dose (a combined dose of 1200 mg — 600 mg of Casirivimab and 600 mg of Imdevimab) will be ₹59,750, inclusive of taxes.