Explained: Delta And Delta Plus COVID Variants And Its Impact

The Delta variant first found in India is now the fastest growing strain in the world and also mutating at the same time

The B.1.617.2 strain that was first found in India and was coined as the Delta strain by the World Health Organisation has further mutated to create a sub-variant called Delta plus that could be more easily transmissible.

The Ministry of Health and Family Welfare reported 40 cases of the mutation in the country from Kerala, Madhya Pradesh, and Maharashtra. They have asked these states to increase surveillance to ensure that this variant does not spread rapidly, leading to an exponential increase in cases.

Rajesh Bhushan, the Health Secretary, in the weekly COVID press conference shared that this Delta plus variant was a variant of interest. The Ministry, however, later stated that all sub-types of the original Delta variant will also be recognised as variants of concern just like B. 1.617.2.

Variants are classified as variants of interest or variants of concern on the basis of their transmissibility and how they reduce the effect of antibodies. VOIs are variants that could reduce neutralisation of antibodies with a predicted increase in transmissibility while VOCs have evidence supporting that they are more easily transmitting among a population along with reducing the effect of vaccines.

The Delta variant that was discovered after a spurt in cases in India, was first acknowledged as a variant of concern by Public Health England. PHE declared it a VOC as it found that most of the new cases post December, when confirmed with genomic sequencing, showed the L452R and T478K mutation synonymous to the Delta variant. This variant does not have the E484Q mutation that is found in most variants of concern.

Scientists have claimed that this variant could also escape vaccine led immunity. Reports from Canada and UK found that fully vaccinated healthcare workers were infected by the Delta variant, giving impetus to the belief of the scientists.

Difference Between Delta And Delta Plus

The Delta variant that spread rapidly around the world was first found in India. PHE on June 11 spoke about a new mutation in B.1.617.2 spike protein wherein the amino lysine (K) has been replaced with an asparagine (N) at the 417th position.

Currently, as of June 18, according to the Health Ministry, there are 205 cases of this new variant, globally. Many of these have been reported from the UK and US.

The Indian genomic sequencing consortium INSACOG has shared that the frequency of this variant also called AY.1 is low in India. There needs to be further research to understand the effects of the variant on vaccination.

Delta Variant- Breakthrough, Infectivity, Transmissibility

American epidemiologist Dr. Eric Feigl-Ding has been tweeting about the Delta variant as the fastest growing variant in both UK and US. He even asked people to be more cautious as this variant is seen to escape immunity induced by vaccines.

Two studies conducted in UK and Scotland and published in the British medical journal the Lancet show that the risk of being infected by the Delta variant is still high after only one dose of the vaccine. The UK study only tested for the Pfizer-BioNTech vaccine while the study in Scotland checked for both Pfizer and Oxford-AstraZeneca.

In Scotland, although the vaccine does act against the Delta variant, the efficacy of both the vaccines are lesser than their efficacy against the original SARS-CoV-2 strain found in Wuhan. While the Pfizer vaccine has a 92 per cent efficacy against the original strain, it has only 79 per cent efficacy against the Delta variant. Similarly, the efficacy of the AstraZeneca vaccine dropped from 79 per cent to 73 per cent. The study also found that this variant doubles the risk of hospitalisation.

Reports of fully vaccinated healthcare workers from Indonesia, Canada with the Delta variant act as evidence for this variant's capacity to increase breakthrough infections. There have been cases of hospitalisation in the breakthrough infections but the severity of the virus has been low.

As for its transmissibility, the variant is the dominant strain in several European countries. Sydney, in Australia, witnessed a new outbreak and strict regulations were imposed in the city after "fleeting encounters" in the same airspace at a mall in Bondi were infected by the Delta variant. Epidemiologists who spoke to the Australian media suggested that this was due to the higher transmissibility of the variant.


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