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Volume 28, Number 8—August 2022
Research

Transmissibility of SARS-CoV-2 B.1.1.214 and Alpha Variants during 4 COVID-19 Waves, Kyoto, Japan, January 2020–June 2021

Yasufumi MatsumuraComments to Author , Miki Nagao, Masaki Yamamoto, Yasuhiro Tsuchido, Taro Noguchi, Koh Shinohara, Satomi Yukawa, Hiromi Inoue, and Takeshi Ikeda
Author affiliations: Kyoto University Graduate School of Medicine, Kyoto, Japan (Y. Matsumura, M. Nagao, M. Yamamoto, Y. Tsuchido, T. Noguchi, K. Shinorara, S. Yukawa); Health and Welfare Bureau of Kyoto City, Kyoto (H. Inoue, T. Ikeda)

Main Article

Table 4

Secondary attack rates and risk factors for SARS-CoV-2 infection in 206 households whose members were infected with SARS-CoV-2 B.1.1.214 or Alpha variants, Kyoto, Japan, November 2020–May 2021*

Variables No. contacts No. infected Secondary attack rate, %
Adjusted odds ratio (95% CI)† p value†
Observed Predicted (IQR)†
Overall
564
328
58.2
58.1 (46.5–71.1)
NA
NA
Index case age group, y
<18 57 23 40.4 40.4 (28.3–49.8) 0.67 (0.35–1.28) 0.22
19–59 419 256 61.1 61.1 (51.7–70.9) Referent
>60
88
49
55.7
55.5 (44.9–64.0)
0.73 (0.44–1.22)
0.23
Contacts age group, y
<18 167 82 49.1 49.1 (37.3–61.9) 0.72 (0.48–1.07) 0.10
19–59 344 208 60.5 60.4 (52.7–70.9) Referent
>60
53
38
71.7
71.9 (66.0–81.0)
1.75 (0.89–3.42)
0.10
Index case symptoms
Asymptomatic 58 19 32.8 32.7 (24.1–43.4) Referent
Symptomatic
506
309
61.1
61.1 (51.7–70.9)
2.84 (1.49–5.42)
<0.01
Household size
2–3 171 123 71.9 71.9 (70.9–78.7) Referent
4 189 112 59.3 59.3 (52.0–69.3) 0.61 (0.38–0.97) 0.04
5 100 43 43.0 42.9 (37.3–47.5) 0.34 (0.20–0.58) <0.01
>6
104
50
48.1
48.0 (44.4–55.3)
0.46 (0.26–0.79)
<0.01
SARS-CoV-2 lineage
Non-VOC, B.1.1.214 282 152 53.9 54.0 (44.9–64.0) Referent
Alpha, B.1.1.7 282 176 62.4 62.3 (55.3–72.7) 1.52 (1.06–2.18) 0.02

*IQR, interquartile range; NA, not applicable; VOC, variant of concern. †Calculated by using a generalized linear mixed-effects logistic regression model.

Main Article

Page created: June 08, 2022
Page updated: July 21, 2022
Page reviewed: July 21, 2022
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