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Explained: Delta and Delta Plus variants of COVID-19

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Even as triple mutant Delta spreads, causing immense concern across the world, the further evolved Delta Plus lurks around the corner. The earliest sequence of the Plus genome was found in Europe in late March. It is still not a 'variant of concern.'

Explained: Delta and Delta Plus variants of COVID-19
As the second wave of COVID-19 hit India in late February-early March, experts partly blamed it on a triple mutant of the novel coronavirus of B.1.617.2 lineage, detected in India around 2020 end. The World Health Organization (WTO) named it Delta on May 31. Now, the highly transmissible variant of Sars-CoV-2 has mutated further to Delta Plus of AY.1 lineage. Scientists added that there is no immediate cause for concern as its incidence in the country is still low.
The government on June 15 said the Delta Plus variant has been around since March this year. However, it is not a variant of concern as yet. Dr V.K. Paul, member (health), NITI Aayog, said its presence has been submitted to the global data system.
What are the Delta Variants?
The Delta variant of the coronavirus is a triple mutant virus as it has split into three lineages. Virologists say the variant has 12 mutations compared to the main B.1 lineage. The key mutations, characterised by the acquisition of K417N mutation in its spike protein, allow the virus to bind better to the cell receptor to enter the human body more efficiently. This increases its ability to multiply and transmit better.
Latest research shows that there are two groups of K417N -- one of them, Delta, has spread internationally and the other one is found on the genome sequences uploaded on global science initiative GISAID by the United States, according to a Hindustan Times report.
By June 7, 63 genomes of Delta Plus variant were identified on GISAID from Canada, Germany, Russia, Nepal, Switzerland, India, Poland, Portugal, Japan and the US. The earliest sequence of this genome was found in Europe in late March this year.
Delta Vs Other Variants
The WHO has elevated the Delta mutant from being a “variant of interest” to “variant of concern,” citing its significantly increased transmissibility in a growing number of countries.
While the Delta variant accounts for over 90 percent of cases in the United Kingdom, 36 cases of the Delta Plus variant have been detected. Two UK cases were registered in persons who received the second vaccine dose more than 14 days ago.
The British government said on June 11 the Delta variant is 60 percent more transmissible in households than Alpha. Subsequently, the UK has delayed its planned relaxations in COVID restrictions by four weeks until July 19.
According to the WHO’s weekly update, the Delta variant is now found in at least 74 countries. In the US, the Delta and its Plus variants account for more than 6 percent of sequenced virus samples, according to data from the US Centers for Disease Control and Prevention (CDC).
Meanwhile, Dr Scott Gottlieb, the former commissioner of the Food and Drug Administration (FDA), said during a TV show on June 13 the Delta strain was likely to become the dominant source of new infections in the US in the Fall. He feared that unvaccinated Americans would be most at risk. “It's doubling every two weeks,” Dr Gottlieb said.
Vaccines Vs Delta
Scientists are yet to test the effectiveness of vaccines on the Delta Plus variant but Dr Gottlieb said the COVID-19 vaccines appeared to be effective at containing the Delta variant, highlighting the importance of public vaccination.
"The mRNA vaccine seems to be highly effective, about 88 percent against the Delta variant. The viral vector vaccines from Johnson & Johnson and AstraZeneca also appear to be about 60 percent effective," he said. The vaccines developed by Moderna and Pfizer/BioNTech use mRNA technology.
A study by Public Health England found that after two doses, the Pfizer vaccine is 88 percent effective, while the AstraZeneca vaccine is 60 percent effective. In India, the AstraZeneca vaccine is being manufactured by Serum Institute of India (SII) as Covishield.
However, both vaccines were only 33 percent effective three weeks after the first dose against symptomatic cases of the Delta variant, compared to 50 percent effective for the Alpha variant, a reminder of how important the second shot is.
Hyderabad-based Bharat Biotech has also stated that their vaccine, Covaxin, works against the variant. A study by the National Institute of Virology in Pune, the Indian Council of Medical Research, and Bharat Biotech has confirmed this.
The study, which is pre-print and has not yet been peer-reviewed, is based on samples from 20 people who recovered from the COVID-19 and 17 who received their second dose of Covaxin at least 28 days prior to the study.
However, a contradictory study by the All India Institute of Medical Sciences on a small group of 63 people suggested that Covishield or Covaxin didn’t work against the variant. Experts say only a “high level of vaccination coverage is the way out of this pandemic.”
The WHO said at least 80 percent COVID-19 vaccination coverage is needed to significantly lower the risk of new variants.
According to government data, around 4 percent of India’s population has been fully vaccinated, while the country has so far given at least one dose to 20.55 crore people, that is 14.31 percent of its population.

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