Assessment of secondary attack rates from paediatric index cases
| Author | Population, country | Paediatric (suspected) index cases | Symptomatic/asymptomatic paediatric index cases | Age of paediatric (suspected) index cases | Contacts of paediatric index cases traced | Secondary positive cases from paediatric index cases | Secondary attack rate from paediatric index cases (positive cases/contacts traced) |
| Abbas and Törnhage 202125 | Two households, Sweden | 1 | One symptomatic | 14 years old | 4 | 3 | 75% |
| Bistaraki et al 202110 | 29 385 index cases and 64 608 contacts, Greece | 1837 0–11 years old: 638 12–17 years old: 1199 | Not mentioned | 0–17 | Overall: 5171I 0–11 years old: 1672 12–17 years old: 3499 | Overall: 958 0–11 years old: 418 12–17 years old: 540 | Overall: 18.5% 0–11 years old: 25.0% (95% CI: 22.2 to 28.0) 12–17 years old: 15.4% (95% CI: 13.9 to 17.1) |
| Calvani et al 202128 | 70 children and 219 family members, Italy | 23 0–5 years old: 4 6–10 years old: 9 11–19 years old: 10 | Not mentioned | 0–19 | Overall: 72 0–5 years old: 12 6–10 years old: 26 11–19 years old: 34 Symptomatic index cases: 41 Asymptomatic index cases: 31 | Overall: 22 0–5 years old: 4 6–10 years old: 6 11–19 years old: 12 Symptomatic index cases: 15 Asymptomatic index cases: 7 | Overall: 30.6% (95% CI: 20.2 to 42.5) 0–5 years old: 33.3% 6–10 years old: 23.1% 11–19 years old: 35.3% Symptomatic index cases: 36.6% Asymptomatic index cases: 22.6% |
| Charbonnier et al 202111 | 34 family clusters, France | 34 | Not mentioned | Median: 7 (IQR, 3–12) | 184 (111 adults, 73 children) | 24 | 13% |
| Galow et al 202112 | 150 households (137 index, 238 contacts), Germany | 17 | Not mentioned | <18 | 41 | 6 | 0–18 years old: 15% (95% CI: 0.05 to 0.27) |
| Hare et al 202126 | one family cluster, Ireland | 1 | One symptomatic | 22-month-old | 9 | 6 | 67% (95% CI: 35 to 88) |
| Koureas et al 202122 | Roma settlement, 40 households, Greece | 9 <12 years old: 3 13–19 years old: 6 | Not mentioned | 0–19 | Overall: 40 <12 years old: 15 13–19 years old: 25 | Overall: 12 <12 years old: 1 13–19 years old: 11 | Overall: 30% <12 years old: 6.67% (95% CI: 0.17 to 31.95) 13–19 years old: 44% (95% CI: 24.40 to 65.07) |
| Kuwelker et al 202127 | 112 households (112 index patients and 179 household members), Norway | 2 | Not mentioned | <20 | 6 | 2 | 0–20 years old: 33% (95% CI: 10 to 70) |
| Loenenbach et al 202113 | 38 households with 92 contact persons, Germany | 22 | Not mentioned | <18 | 59 (15 children, 44 adults) | 23 (4 children, 19 adults) | 39% (95% CI: 28 to 52) |
| Maltezou et al 202116 | 23 family clusters, Greece | 6 (5 infants and one adolescent) | <18 | 0 | 0% | ||
| Miller et al 202117 | 181 households, England | 92 0–10 years old:37 11–18 years old: 55 | Not mentioned | 0–18 | Overall: 155 0–10 years old: 61 11–18 years old: 94 | Overall: 40 0–10 years old: 14 11–18 years old: 26 | Overall: 26% 0–10 years old: 25% (95% CI: 12 to 38) 11–18 years old: 30% (95% CI: 19 to 41) |
| Soriano-Arandes et al 202119 | 1040 paediatric cases linked to 3392 contacts, Spain | 80 0–3 years old: 15 3–6 years old: 14 6–12 years old: 27 12–16 years old: 24 | 67 symptomatic | 283 | 167 | 59% | |
| Stich et al 202123 | 405 households, Germany | 25 0–11.9 years old: 9 12–17.9 years old: 16 | Not mentioned | Overall: 77 0–11.9 years old: 30 12–17.9 years old: 47 | Overall: 19 0–11.9 years old: 4 12–17.9 years old: 15 | Overall: 25% 0–11.9 years old: 12% (95% CI: 0.59 to 11.4) 12–17.9 years old: 30.8% (95% CI: 3.11 to 55.9) | |
| Telle et al 202120 | 7548 families, Norway | 2584 ≤6 years old: 200 7–12 years old: 517 13–16 years old: 781 17–20 years: 1086 | Not mentioned | 6748 | 928 | 14% (95% CI: 13 to 15%) Highest SAR=24% (95% CI :20 to 28) when the index was a child aged 0–6 years Lowest SAR=11% (95% CI: 10 to 13) when a child aged 17–20 was the index case |
SAR, secondary attack rate.