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 Matsumura
, Miki Nagao, Masaki Yamamoto, Yasuhiro Tsuchido, Taro Noguchi, Koh Shinohara, Satomi Yukawa, Hiromi Inoue, and Takeshi Ikeda
, Miki Nagao, Masaki Yamamoto, Yasuhiro Tsuchido, Taro Noguchi, Koh Shinohara, Satomi Yukawa, Hiromi Inoue, and Takeshi Ikeda
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.
Page created: June 08, 2022
Page updated: July 21, 2022
Page reviewed: July 21, 2022
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.