Table 1. Secondary attack rates of SARS-CoV-2 B.1.1.7 variant infections in sub-groups, by type of contact and by age in three childcare centre outbreaks, Hesse, Germany, January–February 2021.
| Childcare centre 1 | Childcare centre 2 | Childcare centre 3 | |||||||
|---|---|---|---|---|---|---|---|---|---|
| n/N | SAR (%) | 95% CI | n/N | SAR (%) | 95% CI | n/N | SAR (%) | 95% CI | |
| Overall SAR | 25/68 | 37 | 26–49 | 12/44 | 27 | 16–42 | 10/59 | 17 | 9–28 |
| 7 days clusteringa | 22/25 | 88 | 70–96 | 10/12 | 83 | 55–95 | 8/10 | 80 | 49–94 |
| Group | |||||||||
| Group 1 (with PC) | 8/15 | 53 | 30–75 | 3/9 | 33 | 12–65 | 6/18 | 33 | 16–56 |
| Group 2 | 7/11 | 64 | 35–85 | 6/15 | 40 | 20–64 | 3/20 | 15 | 5–36 |
| Group 3 | 2/9 | 22 | 6–55 | 1/7 | 14 | 3–51 | NA | – | – |
| Group 4 | 5/16 | 31 | 14–56 | NA | – | – | NA | – | – |
| Daycare | 2/12 | 17 | 5–45 | 0/7 | 0 | 0–35 | 1/15 | 7 | 1–30 |
| Staff | 1/5 | 20 | 4–62 | 2/6 | 33 | 10–70 | 0/6 | 0 | 0–39 |
| Type of contact | |||||||||
| Close contact | 8/15 | 53 | 30–75 | 3/9 | 33 | 12–65 | 9/41 | 22 | 12–37 |
| Non-close contact | 17/53 | 32 | 21–45 | 9/35 | 26 | 14–42 | 1/18 | 6 | 1–26 |
| Age category | |||||||||
| Children | 15/49 | 31 | 20–45 | 7/26 | 27 | 14–46 | 6/36 | 17 | 8–32 |
| Adults | 10/19 | 53 | 32–73 | 5/18 | 28 | 12–51 | 4/23 | 17 | 7–37 |
CI: confidence interval; n: number; N: total number; NA: not applicable; PC: primary case; SAR: secondary attack rates; SARS-CoV-2: severe acute respiratory syndrome coronavirus 2.
a Clustering of secondary cases within an interval of 7 days. For asymptomatic persons (childcare centre 1: n = 7; childcare centre 2: n = 5; childcare centre 3: n = 2) the day of testing was assigned.