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Community Transmission and Viral Load Kinetics of SARS-CoV-2 Delta (B.1.617.2)Variant in Vaccinated and Unvaccinated Individuals

46 Pages Posted: 6 Sep 2021

See all articles by Anika Singanayagam

Anika Singanayagam

Imperial College London

Seran Hakki

Imperial College London

Jake Dunning

Public Health England - Emerging Infections and Zoonoses Unit

Kieran J. Madon

Imperial College London

Michael Crone

Imperial College London - London Biofoundry; Imperial College London - Section of Structural and Synthetic Biology; UK Dementia Research Institute - Care Research and Technology Centre

Aleksandra Koycheva

Imperial College London

Nieves Derqui-Fernandez

Imperial College London

Jack L. Barnett

Imperial College London

Michael G. Whitfield

Imperial College London

Robert Varro

Imperial College London

Andre Charlett

Public Health England Colindale

Rhia Kundu

Imperial College London

Joe Fenn

Imperial College London

Anjna Badhan

Imperial College London

Simon Dustan

Imperial College London

Chitra Tejpal

Imperial College London

Anjeli Vetkar

Imperial College London

Jessica Cutajar

Imperial College London

Valerie Quinn

Imperial College London

Emily Conibear

Imperial College London

Janakan Sam Narean

Imperial College London

Sarah Hammett

Imperial College London

Eimear McDermott

Imperial College London

Timesh Pillay

Imperial College London

Hamish Houston

Imperial College London

Constanta Luca

Imperial College London

Jada Samuel

Imperial College London

Samuel Bremang

Imperial College London

Charlotte Anderson

Government of the United Kingdom - Public Health England

David Jackson

affiliation not provided to SSRN

Shahjahan Miah

Government of the United Kingdom - Public Health England Colindale

Joanna Ellis

Government of the United Kingdom - Public Health England

Angie Lackenby

Virus Reference Department, Public Health England

Wendy S. Barclay

Imperial College London

Paul Freemont

Imperial College London - London Biofoundry

Graham P. Taylor

Department of Infectious Disease, Imperial College London

Shazaad Ahmad

University of Manchester - Manchester University NHS Foundation Trust

Maria Zambon

Public Health England - Virus Reference Department

Neil M. Ferguson

Imperial College London - MRC Centre for Global Infectious Disease Analysis

Ajit Lalvani

Imperial College London

More...

Abstract

Background: The SARS-CoV-2 Delta variant is highly transmissible and spreading globally but a detailed understanding of community transmission risks in highly vaccinated populations is lacking.

Methods: Between September 2020 and August 2021, we recruited 510 community contacts of 422 UK COVID-19 cases to a cohort study. A total of 7194 upper respiratory tract (URT) samples were tested from sequential daily sampling of participants for up to 20 days. We analysed transmission risk by vaccination status for 139 contacts exposed to the Delta variant. We compared viral load (VL) trajectories from fully-vaccinated cases of Delta infection (n=19) with unvaccinated Delta (n=10), Alpha (n=39) and pre-Alpha (n=49) infections.

Findings: The household secondary attack rate for fully-vaccinated contacts exposed to Delta was 19.7% (95%CI:11.6-31.3%), compared with 35.7% (95%CI:16.4-61.2%) in the unvaccinated. One third of infections in Delta-exposed contacts arose from fully-vaccinated index cases and one half of infected contacts were also fully-vaccinated. Seven transmission events between fully vaccinated index-contact pairs occurred. Genomic analysis confirmed transmission pathways between fully-vaccinated individuals within three households. Peak VL was similar in vaccinated and unvaccinated individuals with Delta variant infection but vaccinated Delta cases saw significantly faster VL decline than unvaccinated Alpha or Delta cases. Within infected individuals, faster VL growth was correlated with higher peak VL and slower decline.

Interpretation: Although vaccination reduces the risk of Delta infection and causes some changes to viral kinetics, fully-vaccinated individuals with breakthrough infections have peak URT VL similar to unvaccinated cases and can efficiently transmit infection in household settings, including to fully vaccinated contacts.

Funding: National Institute for Health Research (Award:NIHR200927)

Declaration of Interest: The authors declare no relevant conflicts.

Ethical Approval: The study was approved by the Health Research Authority (Research Ethics Committee reference: 20/NW/0231).

Keywords: SARS-CoV-2, transmission, viral kinetics, breakthrough infection, vaccination

Suggested Citation

Singanayagam, Anika and Hakki, Seran and Dunning, Jake and Madon, Kieran J. and Crone, Michael and Crone, Michael and Koycheva, Aleksandra and Derqui-Fernandez, Nieves and Barnett, Jack L. and Whitfield, Michael G. and Varro, Robert and Charlett, Andre and Kundu, Rhia and Fenn, Joe and Badhan, Anjna and Dustan, Simon and Tejpal, Chitra and Vetkar, Anjeli and Cutajar, Jessica and Quinn, Valerie and Conibear, Emily and Sam Narean, Janakan and Hammett, Sarah and McDermott, Eimear and Pillay, Timesh and Houston, Hamish and Luca, Constanta and Samuel, Jada and Bremang, Samuel and Anderson, Charlotte and Jackson, David and Miah, Shahjahan and Ellis, Joanna and Lackenby, Angie and Barclay, Wendy S. and Freemont, Paul and Taylor, Graham P. and Ahmad, Shazaad and Zambon, Maria and Ferguson, Neil M. and Lalvani, Ajit, Community Transmission and Viral Load Kinetics of SARS-CoV-2 Delta (B.1.617.2)Variant in Vaccinated and Unvaccinated Individuals. Available at SSRN: https://ssrn.com/abstract=3918287 or http://dx.doi.org/10.2139/ssrn.3918287

Anika Singanayagam (Contact Author)

Imperial College London

Seran Hakki

Imperial College London

South Kensington Campus
Exhibition Road
London, SW7 2AZ
United Kingdom

Jake Dunning

Public Health England - Emerging Infections and Zoonoses Unit

United Kingdom

Kieran J. Madon

Imperial College London

South Kensington Campus
Exhibition Road
London, SW7 2AZ
United Kingdom

Michael Crone

Imperial College London - Section of Structural and Synthetic Biology ( email )

Department of Infectious Disease
London, SW7 2AZ
United Kingdom

Imperial College London - London Biofoundry ( email )

Translation and Innovation Hub
84 Wood Lane
London, W12 0BZ
United Kingdom

UK Dementia Research Institute - Care Research and Technology Centre ( email )

Imperial College London
London
United Kingdom

Aleksandra Koycheva

Imperial College London

South Kensington Campus
Exhibition Road
London, SW7 2AZ
United Kingdom

Nieves Derqui-Fernandez

Imperial College London

South Kensington Campus
Exhibition Road
London, SW7 2AZ
United Kingdom

Jack L. Barnett

Imperial College London

South Kensington Campus
Exhibition Road
London, SW7 2AZ
United Kingdom

Michael G. Whitfield

Imperial College London

South Kensington Campus
Exhibition Road
London, SW7 2AZ
United Kingdom

Robert Varro

Imperial College London

South Kensington Campus
Exhibition Road
London, SW7 2AZ
United Kingdom

Andre Charlett

Public Health England Colindale ( email )

61 Colindale Avenue
London, NW9 5EQ
United Kingdom

Rhia Kundu

Imperial College London

South Kensington Campus
Exhibition Road
London, SW7 2AZ
United Kingdom

Joe Fenn

Imperial College London

Anjna Badhan

Imperial College London

South Kensington Campus
Exhibition Road
London, SW7 2AZ
United Kingdom

Simon Dustan

Imperial College London

South Kensington Campus
Exhibition Road
London, SW7 2AZ
United Kingdom

Chitra Tejpal

Imperial College London

South Kensington Campus
Exhibition Road
London, SW7 2AZ
United Kingdom

Anjeli Vetkar

Imperial College London

South Kensington Campus
Exhibition Road
London, SW7 2AZ
United Kingdom

Jessica Cutajar

Imperial College London

South Kensington Campus
Exhibition Road
London, SW7 2AZ
United Kingdom

Valerie Quinn

Imperial College London

South Kensington Campus
Exhibition Road
London, SW7 2AZ
United Kingdom

Emily Conibear

Imperial College London

South Kensington Campus
Exhibition Road
London, SW7 2AZ
United Kingdom

Janakan Sam Narean

Imperial College London

South Kensington Campus
Exhibition Road
London, SW7 2AZ
United Kingdom

Sarah Hammett

Imperial College London

South Kensington Campus
Exhibition Road
London, SW7 2AZ
United Kingdom

Eimear McDermott

Imperial College London

South Kensington Campus
Exhibition Road
London, SW7 2AZ
United Kingdom

Timesh Pillay

Imperial College London

South Kensington Campus
Exhibition Road
London, SW7 2AZ
United Kingdom

Hamish Houston

Imperial College London

South Kensington Campus
Exhibition Road
London, SW7 2AZ
United Kingdom

Constanta Luca

Imperial College London

South Kensington Campus
Exhibition Road
London, SW7 2AZ
United Kingdom

Jada Samuel

Imperial College London

South Kensington Campus
Exhibition Road
London, SW7 2AZ
United Kingdom

Samuel Bremang

Imperial College London

South Kensington Campus
Exhibition Road
London, SW7 2AZ
United Kingdom

Charlotte Anderson

Government of the United Kingdom - Public Health England

Wellington House
133-155 Waterloo Road
London, SE1 8UG
United Kingdom

David Jackson

affiliation not provided to SSRN

Shahjahan Miah

Government of the United Kingdom - Public Health England Colindale

61 Colindale Avenue
London, NW9 5EQ
United Kingdom

Joanna Ellis

Government of the United Kingdom - Public Health England ( email )

Wellington House
133-155 Waterloo Road
London, SE1 8UG
United Kingdom

Angie Lackenby

Virus Reference Department, Public Health England

Wendy S. Barclay

Imperial College London

Paul Freemont

Imperial College London - London Biofoundry ( email )

Translation and Innovation Hub
84 Wood Lane
London, W12 0BZ
United Kingdom

Graham P. Taylor

Department of Infectious Disease, Imperial College London ( email )

Shazaad Ahmad

University of Manchester - Manchester University NHS Foundation Trust

Oxford Road
Manchester, M13 9PL
United Kingdom

Maria Zambon

Public Health England - Virus Reference Department ( email )

Wellington House
133-155 Waterloo Road
London, SE1 8UG
United Kingdom

Neil M. Ferguson

Imperial College London - MRC Centre for Global Infectious Disease Analysis ( email )

South Kensington Campus
Exhibition Road
London, Greater London SW7 2AZ
United Kingdom

Ajit Lalvani

Imperial College London

South Kensington Campus
Exhibition Road
London, SW7 2AZ
United Kingdom

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