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Volume 28, Number 6—June 2022
Dispatch

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, and Adrian Aginagalde-Llorente
Author affiliations: University Hospital of Móstoles, Madrid, Spain (J. Del Águila-Mejía); Public Health Observatory of Cantabria, Santander, Spain (J. Del Águila-Mejía, A. Aginagalde-Llorente); Directorate General of Public Health, Government of Cantabria, Santander (R. Wallmann); Marqués de Valdecilla University Hospital, Santander (J. Calvo-Montes, J. Rodríguez-Lozano, T. Valle-Madrazo)

Main Article

Table 2

Comparison of Omicron and Delta variant of SARS-CoV-2 transmission period, incubation period, and serial interval by index case-patient vaccination status, Spain*

Characteristic
 Mean (SD)
Median (IQR)
Omicron
 Delta
 Difference (95% CI)†
 p value
 Omicron
 Delta
Transmission period 0.5 (2.3) 0.8 (2.6) −0.3 (−0.56 to −0.02) 0.04 0 (−1 to –2) 1 (−1 to 2)
Unvaccinated index case-patient 0.5 (2.3) 0.7 (2.5) −0.2 (−0.6 to 0.14) 0.22 1 (−1 to 2)
Vaccinated index case-patient
 0.6 (2.3)
 0.9 (2.7)
 −0.3 (−0.7 to 0.14)
 0.89
0 (−1 to 2)
Incubation period 3.1 (2.6) 3.3 (2.7) −0.2 (−0.6 to 0.16) 0.29 3 (1–4) 3 (1–5)
Unvaccinated index case-patient 3.1 (2.7) 3.3 (2.6) −0.2 (−0.7 to 0.3) 0.46 3 (1–4)
Vaccinated index case-patient
 3 (2.2)
 3.4 (2.9)
 −0.4 (−0.9 to 0.14)
 0.16
3 (2–4)
Serial interval 4.8 (3) 5.4 (3.1) −0.6 (−1 to −0.15) 0.008 4 (3–6) 5 (3–8)
Unvaccinated index case-patient 4.7 (3.1) 5.4 (3.1) −0.7 (−1.3 to −0.06) 0.02 5 (3–8)
Vaccinated index case-patient 4.9 (3.1) 5.3 (3.1) −0.4 (−1 to 0.28) 0.26 5 (3–7)

*IQR, interquartile range. †Student t test for difference in mean of Delta and Omicron period.

Main Article

Page created: March 23, 2022
Page updated: May 22, 2022
Page reviewed: May 22, 2022
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