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. 2022 Jun;28(6):1224-1228.
doi: 10.3201/eid2806.220158. Epub 2022 Apr 7.

Secondary Attack Rate, Transmission and Incubation Periods, and Serial Interval of SARS-CoV-2 Omicron Variant, Spain

Javier Del Águila-Mejía, Reinhard Wallmann, Jorge Calvo-Montes, Jesús Rodríguez-Lozano, Trinidad Valle-Madrazo, Adrian Aginagalde-Llorente

Secondary Attack Rate, Transmission and Incubation Periods, and Serial Interval of SARS-CoV-2 Omicron Variant, Spain

Javier Del Águila-Mejía et al. Emerg Infect Dis. 2022 Jun.

Abstract

Contact tracing data of SARS-CoV-2 Omicron variant cases during December 2021 in Cantabria, Spain, showed increased transmission (secondary attack rate 39%) compared with Delta cases (secondary attack rate 26%), uninfluenced by vaccination status. Incubation and serial interval periods were also reduced. Half of Omicron transmissions happened before symptom onset in the index case-patient.

Keywords: COVID-19; Omicron variant; SARS-CoV-2; Spain; coronavirus disease; incubation period; respiratory infections; secondary attack rate; severe acute respiratory syndrome coronavirus 2; surveillance; viruses; zoonoses.

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Figures

Figure 1
Figure 1
Distribution of Omicron variant SARS-CoV-2 cases, Cantabria, Spain, December 2021. A) Transmission period; B) incubation period; C) serial interval. Each panel shows case density over time (top), a typical boxplot (middle), and cumulative distribution for the period (bottom). For the boxplot, the center line indicates the median, the box left and right ends the interquartile range, the error bars 95% CI, and the open circles outliers. SOD, symptom onset date.
Figure 2
Figure 2
Transmission period distribution for Omicron and Delta variant SARS-CoV-2 cases by vaccination and symptom status, Cantabria, Spain. SOD, symptom onset date.
See this image and copyright information in PMC

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Supplementary concepts