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Volume 29, Number 8—August 2023
Dispatch

SARS-CoV-2 Variants and Age-Dependent Infection Rates among Household and Nonhousehold Contacts

Reiko MiyaharaComments to Author , Kosuke Tamura, Tomoko Kato, Mineko Nakazaki, Kanako Otani, Yura K. Ko, Taro Kamigaki, Yuzo Arima, Hideki Tani, Kazunori Oishi, and Motoi Suzuki
Author affiliations: National Institute of Infectious Diseases, Tokyo, Japan (R. Miyahara, K. Otani, T. Kamigaki, Y. Arima, M. Suzuki); Toyama Institute of Health, Toyama, Japan (K. Tamura, M. Nakazaki, H. Tani, K. Oishi); Takaoka Health and Welfare Center, Toyama (T. Kato); Tohoku University Graduate School of Medicine, Miyagi, Japan (Y.K. Ko)

Main Article

Table

Infection rates of SARS-CoV-2 infection among household and nonhousehold contacts in study of SARS-CoV-2 variants and age-dependent infection rates

Variable Household contacts
 Nonhousehold contacts
Total no. No. PCR positive Infection rate, % Adjusted odds ratio (95% CI)* Total no. No. PCR positive Infection rate, % Adjusted odds ratio (95% CI)*
Total
 1,144
 294
 25.7
2,318
 302
 13.0
Period
Pre-VOC 155 20 12.9 Referent 330 36 10.9 Referent
Alpha 251 48 19.1 1.91
(0.94–3.90)		 708 71 10.0 1.47
(0.86–2.50)
Delta 329 83 25.2 3.75
(1.84–7.61)		 544 84 15.4 2.34
(1.37–3.98)
Omicron
 409
 143
 35.0
 6.22
(3.04–12.70)
736
 111
 15.1
 3.55
(2.09–6.06)
Index case-patient age, y
0–19 214 54 25.2 0.42
(0.20–0.86)		 852 34 4.0 0.16
(0.08–0.34)
20–39 493 111 22.5 0.36
(0.20–0.66)		 973 182 18.7 0.42
(0.25–0.73)
40–59 309 84 27.2 0.45
(0.24–0.83)		 317 48 15.1 0.40
(0.22–0.72)
>60
 129
 45
 35.2
 Referent
176
 38
 21.6
 Referent
Close contact age, y
0–19 295 80 27.1 1.06
(0.70–1.62)		 831 45 5.4 0.67
(0.39–1.17)
20–39 259 79 30.5 1.33
(0.89–2.00)		 721 162 22.5 1.09
(0.70–1.71)
40–59 359 84 23.4 1.14
(0.78–1.68)		 353 38 10.8 0.52
(0.31–0.85)
>60 227 51 22.5 Referent 257 51 19.8 Referent
Unknown 4 0 0 NA 156 6 3.8 0.22
(0.07–0.66)

* Odds ratios were adjusted for age, sex, symptoms of index case-patients at the time of diagnosis, contact history, interval from diagnosis of index case-patient to PCR tests, and number of persons in the same household. NA, not applicable; VOC, variant of concern.

Main Article

Page created: June 12, 2023
Page updated: July 19, 2023
Page reviewed: July 19, 2023
The conclusions, findings, and opinions expressed by authors contributing to this journal do not necessarily reflect the official position of the U.S. Department of Health and Human Services, the Public Health Service, the Centers for Disease Control and Prevention, or the authors' affiliated institutions. Use of trade names is for identification only and does not imply endorsement by any of the groups named above.
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