Table 2.
Secondary PCR confirmed SARS-CoV-2 infections in non-index family members within 7 days after index sampling date (SAR7)
| Characteristics of the index case | Overall | Among parents | Among children | Family members tested | ||||
|---|---|---|---|---|---|---|---|---|
| SAR7 | Numerator/denominator | SAR7 | Numerator/denominator | SAR7 | Numerator/denominator | Rate | Numerator/denominator | |
| Overall | 21 (20–21) | 4030/19,443 | 24 (23–25) | 1723/7219 | 19 (18–20) | 2307/12,224 | 69 (69–70) | 13,477/19,443 |
| Parents | 24 (24–25) | 3102/12,695 | 35 (33–36) | 1113/3196 | 21 (20–22) | 1989/9499 | 65 (64–66) | 8215/12,695 |
| Mother | 23 (23–24) | 1705/7266 | 33 (30–35) | 506/1543 | 21 (20–22) | 1199/5723 | 65 (63–66) | 4688/7266 |
| Father | 26 (25–27) | 1397/5429 | 37 (34–39) | 607/1653 | 21 (20–22) | 790/3776 | 65 (64–66) | 3527/5429 |
| Age groups (years) | ||||||||
| ≤ 30 | 17 (15–20) | 152/888 | 34 (28–41) | 66/192 | 12 (10–15) | 86/696 | 56 (53–59) | 497/888 |
| 31–40 | 22 (20–23) | 1011/4702 | 32 (29–35) | 352/1094 | 18 (17–20) | 659/3608 | 62 (60–63) | 2894/4702 |
| 41–50 | 26 (25–28) | 1357/5161 | 36 (33–39) | 467/1301 | 23 (22–24) | 890/3860 | 69 (67–70) | 3544/5161 |
| ≥50 | 30 (28–32) | 582/1944 | 37 (34–41) | 228/609 | 27 (24–29) | 354/1335 | 66 (64–68) | 1280/1944 |
| Children | 14 (13–15) | 928/6748 | 15 (14–16) | 610/4023 | 12 (11–13) | 318/2725 | 78 (77–79) | 5262/6748 |
| Daughter | 13 (12–14) | 436/3406 | 14 (12–15) | 280/2025 | 11 (10–13) | 156/1381 | 78 (77–79) | 2659/3406 |
| Son | 15 (14–16) | 492/3342 | 17 (15–18) | 330/1998 | 12 (10–14) | 162/1344 | 78 (76–79) | 2603/3342 |
| Age groups (years) | ||||||||
| ≤ 6 | 24 (20–28) | 116/487 | 27 (22–33) | 79/290 | 19 (14–25) | 37/197 | 89 (86–92) | 435/487 |
| 7–12 | 14 (12–15) | 198/1455 | 18 (15–20) | 141/803 | 9 (7–11) | 57/652 | 86 (84–87) | 1246/1455 |
| 13–16 | 14 (13–16) | 304/2109 | 16 (14–18) | 191/1198 | 12 (10–15) | 113/911 | 85 (83–86) | 1790/2109 |
| 17–20 | 11 (10–13) | 310/2697 | 11 (10–13) | 199/1732 | 12 (10–14) | 111/965 | 66 (65–68) | 1791/2697 |
| Members in family | ||||||||
| 2 | 15 (13–17) | 214/1427 | 12 (10–15) | 59/484 | 16 (14–19) | 155/943 | 64 (61–66) | 907/1427 |
| 3 | 22 (20–23) | 1011/4698 | 25 (23–27) | 528/2098 | 19 (17–20) | 483/2600 | 68 (67–70) | 3217/4698 |
| 4 | 20 (19–21) | 1393/7059 | 24 (22–25) | 663/2820 | 17 (16–18) | 730/4239 | 71 (70–72) | 5011/7059 |
| 5 | 21 (19–22) | 832/4044 | 25 (23–27) | 321/1290 | 19 (17–20) | 511/2754 | 71 (69–72) | 2852/4044 |
| 6 or more | 25 (23–27) | 379/1510 | 27 (23–32) | 105/387 | 24 (22–27) | 274/1123 | 66 (64–69) | 1000/1510 |
The data include all families in Norway consisting of at least one parent and one child, with at least one family member positive for SARS-CoV-2 in a PCR test in 2020. Percent (95% CI) and absolute numbers
Secondary attack rate (SAR7) was calculated as the number of non-index family members who tested positive within 7 days after the date when the index family member tested positive, divided by all non-index family members, multiplied by 100. Percentage tested was calculated as the number of non-index family members who were tested within 7 days after the date when the index family member tested positive, divided by all non-index family members. 95% CIs around the estimated secondary infection rates and percentage tested were calculated using the Wilson method