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Increased Infectivity, Ability To Escape Immunity Drove Delta Variant Of COVID-19: Study

The international team of researchers combined lab-based experiments and epidemiology of vaccine breakthrough infections, showing that the Delta variant of COVID-19 is better at replicating and spreading than other commonly-observed variants

Increased Infectivity, Ability To Escape Immunity Drove Delta Variant Of COVID-19: Study
Highlights
  • The B.1.617.2 or Delta variant was first observed in India in late 2020
  • The Delta variant caused the second COVID wave in India: Government
  • The Delta variant has spread widely to become dominant worldwide: Expert

New Delhi: The Delta variant of the SARS-CoV-2 virus, which has become the dominant strain in India and many other countries, most likely spread through its ability to evade neutralising antibodies and increased infectivity, according to a study published in the Nature Journal on Tuesday (September 7). The B.1.617.2 or Delta variant was first observed in India in late 2020. It has since spread around the globe. The international team of researchers combined lab-based experiments and epidemiology of vaccine breakthrough infections, showing that the Delta variant is better at replicating and spreading than other commonly-observed variants.

Also Read: How Prepared Is India For COVID-19 Third Wave

There’s also evidence that neutralising antibodies produced as a result of previous infection or vaccination are less effective at stopping this variant, said Professor Ravindra Gupta from the University of Cambridge in the UK, and one of the study’s senior authors.

“These factors are likely to have contributed to the devastating epidemic wave in India during the first quarter of 2021, where as many as half of the cases were individuals who had previously been infected with an earlier variant,” Professor Gupta noted.

To examine how well the Delta variant was able to evade the immune response, the team extracted serum from blood samples collected as part of the COVID-19 cohort of the UK’s National Institute for Health Research (NIHR) BioResource. The samples came from individuals who had previously been infected with the coronavirus or who had been vaccinated with either the Oxford/AstraZeneca, known as Covishield in India, or Pfizer vaccines. Serum contains antibodies raised in response to infection or vaccination.

The team found that the Delta variant virus was 5.7-fold less sensitive to the sera from previously-infected individuals, and as much as eight-fold less sensitive to vaccine sera, compared with the Alpha variant. In other words, it takes eight times as many antibodies from a vaccinated individual to block the virus.

Also Read: COVID Vaccines Effective Against Delta Variant, UK Study Finds

The researchers also analysed over 100 infected healthcare workers at three Delhi hospitals, nearly all of whom had been vaccinated against SARS-CoV-2. They found the Delta variant to be transmitted between vaccinated staff to a greater extent than the Alpha variant.

The Delta variant has spread widely to become the dominant variants worldwide because it is faster to spread and better at infecting individuals than most other variants we have seen, said Partha Rakshit from the National Centre for Disease Control, Delhi, and joint senior author of the study.

“It is also better at getting around existing immunity — either through previous exposure to the virus or to vaccination — though the risk of moderate to severe disease is reduced in such cases,” Mr Rakshit said.

The spike proteins of the SARS-CoV-2 bind to ACE2, a protein receptor found on the surface of cells in our body. Both the spike protein and ACE2 are then cleaved, allowing genetic material from the virus to enter the host cell. The virus manipulates the host cell’s machinery to allow the virus to replicate and spread. Using 3D airway organoids – ‘mini-organs’ grown from cells from the airway, which mimic its behaviour – the team studied what happens when the virus reaches the respiratory tract. The researchers used both a live virus and a ‘pseudotyped virus’ – a synthetic form of the virus that mimicked key mutations on the Delta variant – and used this to infect the organoids.

Also Read: COVID-19 Vaccines Effective At Reducing Severe Illness, Hospitalisation: Lancet Study

They found that the Delta variant was more efficient at breaking into the cells compared with other variants as it carried a larger number of cleaved spikes on its surface. Once inside the cells, the variant was also better able to replicate. Both of these factors give the virus a selection advantage compared to other variants, helping explain why it has become so dominant, according to the researchers.

Professor Anurag Agrawal from the CSIR Institute of Genomics and Integrative Biology, Delhi, India, joint senior author of the study, noted that infection of vaccinated healthcare workers with the Delta variant is a significant problem.

Although they themselves may only experience mild COVID, they risk infecting individuals who have suboptimal immune responses to vaccination due to underlying health conditions and these patients could then be at risk of severe disease, Mr Agrawal said.

“We urgently need to consider ways of boosting vaccine responses against variants among healthcare workers. It also suggests infection control measures will need to continue in the post-vaccine era,” he added.

Also Read: COVID-19 Explainer: What Is The New Covid Variant “Mu”? WHO Warns It Could Be More Resistant To Vaccines

(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)

NDTV – Dettol Banega Swasth India campaign is an extension of the five-year-old Banega Swachh India initiative helmed by Campaign Ambassador Amitabh Bachchan. It aims to spread awareness about critical health issues facing the country. In wake of the current COVID-19 pandemic, the need for WASH (WaterSanitation and Hygiene) is reaffirmed as handwashing is one of the ways to prevent Coronavirus infection and other diseases. The campaign highlights the importance of nutrition and healthcare for women and children to prevent maternal and child mortality, fight malnutrition, stunting, wasting, anaemia and disease prevention through vaccines. Importance of programmes like Public Distribution System (PDS), Mid-day Meal Scheme, POSHAN Abhiyan and the role of Aganwadis and ASHA workers are also covered. Only a Swachh or clean India where toilets are used and open defecation free (ODF) status achieved as part of the Swachh Bharat Abhiyan launched by Prime Minister Narendra Modi in 2014, can eradicate diseases like diahorrea and become a Swasth or healthy India. The campaign will continue to cover issues like air pollutionwaste managementplastic banmanual scavenging and sanitation workers and menstrual hygiene

World

24,24,98,327Cases
20,40,54,102Active
3,35,14,449Recovered
49,29,776Deaths
Coronavirus has spread to 195 countries. The total confirmed cases worldwide are 24,24,98,327 and 49,29,776 have died; 20,40,54,102 are active cases and 3,35,14,449 have recovered as on October 22, 2021 at 5:24 am.

India

3,41,43,236 15,786Cases
1,75,7453,086Active
3,35,14,449 18,641Recovered
4,53,042 231Deaths
In India, there are 3,41,43,236 confirmed cases including 4,53,042 deaths. The number of active cases is 1,75,745 and 3,35,14,449 have recovered as on October 22, 2021 at 2:30 am.

State Details

State Cases Active Recovered Deaths
Maharashtra

65,98,218 1,573

27,899 1,434

64,30,394 2,968

1,39,925 39

Kerala

48,88,523 8,733

82,093 1,240

47,79,228 9,855

27,202 118

Karnataka

29,84,849 365

9,017 86

29,37,848 443

37,984 8

Tamil Nadu

26,91,797 1,164

13,790 268

26,42,039 1,412

35,968 20

Andhra Pradesh

20,62,303 493

5,500 66

20,42,476 552

14,327 7

Uttar Pradesh

17,10,068 10

107 5

16,87,062 14

22,899 1

West Bengal

15,83,646 833

7,535 44

15,57,090 775

19,021 14

Delhi

14,39,488 22

311 1

14,14,087 21

25,090

Odisha

10,37,056 524

4,336 51

10,24,422 573

8,298 2

Chhattisgarh

10,05,773 38

206 21

9,91,995 16

13,572 1

Rajasthan

9,54,395 2

36 2

9,45,405 4

8,954

Gujarat

8,26,353 13

156 20

8,16,110 33

10,087

Madhya Pradesh

7,92,721 12

88 6

7,82,110 6

10,523

Haryana

7,71,125 9

131 2

7,60,945 11

10,049

Bihar

7,26,042 6

30 0

7,16,351 6

9,661

Telangana

6,69,739 183

3,967 1

6,61,829 183

3,943 1

Assam

6,07,811 384

3,762 152

5,98,087 228

5,962 4

Punjab

6,02,135 22

226 6

5,85,358 27

16,551 1

Jharkhand

3,48,526 40

166 24

3,43,225 16

5,135

Uttarakhand

3,43,787 14

176 0

3,36,213 14

7,398

Jammu And Kashmir

3,31,386 87

814 14

3,26,143 73

4,429

Himachal Pradesh

2,22,138 202

1,452 58

2,16,955 140

3,731 4

Goa

1,77,765 59

618 21

1,73,790 35

3,357 3

Puducherry

1,27,564 43

454 7

1,25,258 50

1,852

Manipur

1,23,051 81

1,346 14

1,19,800 94

1,905 1

Mizoram

1,15,944 737

10,034 229

1,05,510 962

400 4

Tripura

84,369 18

105 10

83,448 8

816

Meghalaya

83,210 52

735 26

81,034 76

1,441 2

Chandigarh

65,315 3

26 2

64,469 1

820

Arunachal Pradesh

55,065 22

140 2

54,645 20

280

Sikkim

31,819 19

185 10

31,241 9

393

Nagaland

31,670 11

250 5

30,743 15

677 1

Ladakh

20,896 10

43 9

20,645 1

208

Dadra And Nagar Haveli

10,678 2

4 2

10,670

4

Lakshadweep

10,365

0 0

10,314

51

Andaman And Nicobar Islands

7,646

7 0

7,510

129

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