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Delta variant of Covid-19

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    Science & Technology
  • Published
    7th Jun, 2021


Multiple SARS-CoV-2 variants are circulating globally and B.1.617 lineage, detected in India and has been named as Delta variant of Covid-19 by WHO.

About Delta variant risk assessment

  • Public Health England (PHE) has said a staggering 61% of the samples sequenced are now of the Delta variant (B.1.617.2).
  • This means the Delta variant, first detected in India, is more dominant in the UK than the Alpha variant that had last year triggered a surge in the UK.

What is the Delta variant of Covid-19?

  • Multiple SARS-CoV-2 variants are circulating globally.
  • 1.617 lineage was detected in India earlier this year.
    • its sub-lineage B.1.617.2, known as the Delta variant, is more transmissible than contemporary lineages.
  • The World Health Organizaton (WHO) has given it the label Delta.
  • It has been categorised as a variant of concern (VOC).
    • There is a “significantly increased transmissibility” and a “growing number of countries reporting outbreaks associated with this variant”.

Variant of concern (VOC)

  • WHO classifies a variant as a VOC
    • when it is associated with an increase in transmissibility or detrimental change in Covid-19 epidemiology; increase in virulence; or decrease in the effectiveness of public health measures or available diagnostics, vaccines, therapeutics.

What makes the Delta variant a VOC?

  • The Delta variant contains multiple mutations in the spike protein. At least four mutations are important.
    • One of these is called L452R, this mutation has been found more transmissible than wild-type strains and also been associated with reduced antibody efficacy and reduced neutralisation by vaccine sera.
    • The mutation P681R has been associated with chemical processes that may enhance transmissibility.
    • The D614G mutation was first documented in the US early in the pandemic, having initially circulated in Europe.
    • T478K was present in around 65% of occurrences in variant B.1.1.222, first detected in Mexico last year and associated with higher infectivity.

Effectiveness of vaccines

  • There is a reduction in vaccine effectiveness for Delta compared to Alpha.
  • Pfizer-BioNTech vaccine are likely to have more than five times lower levels of neutralising antibodies against the Delta variant than against other variants.


  • The latest analysis of 874 cases of reinfection in the UK shows that 556 were of Alpha variant, and only 96 were with the Delta variant.