Increased transmissibility of SARS-CoV-2 lineage B.1.1.7 by age and viral load

Zealand University Hospital, Sydvestjysk Sygehus, The Danish Covid-19 Genome Consortium, AAU Coordination, AAU Laboratory, AAU Bioinformatics, AAU CLAUDIA/IT, AAU Legal and Admin, AAU SUND, AAU Computer Science, Statens Serum Institut, Aalborg University Hospital, Rigshospitalet, Hvidovre Hospital, Aarhus University Hospital, Odense University Hospital, Herlev Hospital, Sygehus Lillebælt

Research output: Contribution to journalArticlepeer-review


New lineages of SARS-CoV-2 are of potential concern due to higher transmissibility, risk of severe outcomes, and/or escape from neutralizing antibodies. Lineage B.1.1.7 (the Alpha variant) became dominant in early 2021, but the association between transmissibility and risk factors, such as age of primary case and viral load remains poorly understood. Here, we used comprehensive administrative data from Denmark, comprising the full population (January 11 to February 7, 2021), to estimate household transmissibility. This study included 5,241 households with primary cases; 808 were infected with lineage B.1.1.7 and 4,433 with other lineages. Here, we report an attack rate of 38% in households with a primary case infected with B.1.1.7 and 27% in households with other lineages. Primary cases infected with B.1.1.7 had an increased transmissibility of 1.5–1.7 times that of primary cases infected with other lineages. The increased transmissibility of B.1.1.7 was multiplicative across age and viral load.

Original languageEnglish
Article number7251
JournalNature Communications
Issue number1
StatePublished - Dec 2021
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2021, The Author(s).

ASJC Scopus subject areas

  • General Chemistry
  • General Biochemistry, Genetics and Molecular Biology
  • General Physics and Astronomy


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