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Volume 28, Number 10—October 2022
Research

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 VallèsComments to Author 
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)

Main Article

Table 2

Crude and adjusted risk factors for infection among contacts in the Omicron-dominant period in a study of SARS-CoV-2 secondary attack rates in vaccinated and unvaccinated household contacts during replacement of Delta with Omicron variant, Spain*

Variable No. patients† Crude OR
Adjusted OR‡
OR (95% CI) p value OR (95% CI) p value
Vaccination status, contacts
Vaccinated 135/170 Referent Referent
Unvaccinated 39/45 1.69 (0.7–4.3) 0.3 1.86 (0.6–6.2) 0.3
1 dose 25/29 Referent Referent
2 doses 90/113 0.63 (0.2–2.0) 0.4 0.75 (0.2–2.9) 0.7
3 doses 19/27 0.38 (0.1–1.5) 0.2 0.36 (0.1–1.9) 0.2
Missing data
1/1





Time since vaccination, wk
1–13 36/48 Referent Referent
14–20 28/35 1.33 (0.5–3.8) 0.6 2.17 (0.5–9.3) 0.3
21–25 34/41 1.62 (0.6–4.6) 0.4 2.41 (0.7–7.8) 0.1
>25 36/45 1.33 (0.5–3.6) 0.6 1.91 (0.6–5.7) 0.2
Missing data 1/1
Pooled

1.12 (0.8–1.5)
0.5

1.26 (0.9–1.8)
0.2
Age of contacts, y
0–12 36/42 Referent Referent
13/18 22/27 0.73 (0.2–2.7) 0.6 0.99 (0.2–4.4) 0.9
19/35 38/47 0.70 (0.2–2.2) 0.5 0.94 (0.2–3.8) 0.9
36/45 33/42 0.61 (0.2–1.9) 0.4 0.83 (0.2–3.3) 0.8
>45 45/57 0.63 (0.2–1.8) 0.4 0.82 (0.2–3.2) 0.8
Pooled

0.90 (0.7–1.1)
0.4

0.94 (0.7–1.2)
0.6
Vaccination status, index patients
Vaccinated 134/161 Referent Referent
Unvaccinated
40/54
0.56 (0.3–1.2)
0.1

0.98 (0.2–3.9)
0.9
Age of index patients, y
0–12 36/50 Referent Referent
13–18 13/15 2.53 (0.5–12.7) 0.3 2.79 (0.4–20.4) 0.3
19–35 35/44 1.51 (0.6–3.9) 0.4 1.47 (0.4–5.8) 0.6
36–45 51/59 2.48 (0.9–6.5) 0.07 2.27 (0.5–10.5) 0.3
>45 39/47 1.90 (0.7–5.0) 0.2 1.84 (0.4–8.8) 0.4
Pooled

1.20 (0.9–1.5)
0.1

1.09 (0.8–1.5)
0.6
Number of housemates
<2 60/70 Referent Referent
>2
114/145
0.61 (0.3–1.3)
0.2

0.62 (0.3–1.4)
0.3
Sex
M 93/115 Referent Referent
F 81/100 1.13 (0.7–1.9) 0.6 0.97 (0.5–2.0) 0.9

*OR, odds ratio. †Values are number infected/total number of patients in each strata. ‡Adjusted analysis only included participants who had all data available.

Main Article

Page created: August 11, 2022
Page updated: September 20, 2022
Page reviewed: September 20, 2022
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