SARS-CoV-2 Secondary Attack Rates in Vaccinated and Unvaccinated Household Contacts during Replacement of Delta with Omicron Variant, Spain
Israel López-Muñoz, Ariadna Torrella, Olga Pérez-Quílez, Amaia Castillo-Zuza, Elisa Martró, Antoni E. Bordoy, Verónica Saludes, Ignacio Blanco, Laura Soldevila, Oriol Estrada, Lluís Valerio, Sílvia Roure, and Xavier Vallès
Author affiliations: North Metropolitan International Health Program, Catalan Institute of Health (PROSICS), Badalona, Spain (I. López-Muñoz, A. Torrella, O. Pérez-Quílez, A. Castillo-Zuza, L. Soldevila, L. Valerio, S. Roure, X. Vallès); Hospital Universitari Germans Trias i Pujol, Badalona (E. Martró, A.E. Bordoy, V. Saludes, I. Blanco, L. Soldevila, S. Roure); Center for Biomedical Research in Epidemiology and Public Health (CIBEREPS), Instituto de Salud Carlos III, Madrid, Spain (E. Martró, A.E. Bordoy, V. Saludes); Institut d’Investigació en Ciències de la Salut Germans Trias i Pujol, Badalona (E. Martró, A.E. Bordoy, V. Saludes, I. Blanco, O. Estrada, X. Vallès); Fundació Lluita contra la Sida i les Malalties Transmissibles, Badalona (L. Soldevila, S. Roure, X. Vallès)
Figure 1. Dominance of infection with SARS-CoV-2 Delta and Omicron variants in a study of secondary attack rates in vaccinated and unvaccinated household contacts, Spain. The study population was located in the northern part of the greater metropolitan area of Barcelona, Spain. Genotyping of 1,554 samples from patients with SARS-CoV-2 infections was conducted during November 23, 2020–February 8, 2021 to identify the dominant variant infecting the population. The cutoff date between the Delta and Omicron predominance periods was December 21, 2021.
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