Impact of Distancing on Secondary SARS-CoV-2 Transmission
| . | Districtsa . | Students . | Student Primary Infections . | Student Secondary Infections . | Secondary/Primary Infection Ratiob . | Relative Rate of Secondary Transmissionc . | 95% CIsd . |
|---|---|---|---|---|---|---|---|
| Bus practice (children per seat) | |||||||
| 1 | 13 | 36 975 | 190 | 12 | 0.06 | — | — |
| 2 | 17 | 656 444 | 4388 | 210 | 0.05 | 0.76 | 0.19–2.96 |
| 3 | 17 | 205 996 | 1758 | 83 | 0.04 | 0.75 | 0.18–3.19 |
| Othere | 6 | 43 519 | 353 | 25 | 0.07 | 1.12 | 0.27–4.71 |
| Distancing, ft | |||||||
| 6 | 10 (9%) | 54 557 | 276 | 12 | 0.04 | — | — |
| 3 | 76 (67%) | 610 236 | 4140 | 207 | 0.05 | 1.15 | 0.31–4.24 |
| <3 | 27 (24%) | 278 141 | 2273 | 111 | 0.05 | 1.12 | 0.28–4.45 |
| . | Districtsa . | Students . | Student Primary Infections . | Student Secondary Infections . | Secondary/Primary Infection Ratiob . | Relative Rate of Secondary Transmissionc . | 95% CIsd . |
|---|---|---|---|---|---|---|---|
| Bus practice (children per seat) | |||||||
| 1 | 13 | 36 975 | 190 | 12 | 0.06 | — | — |
| 2 | 17 | 656 444 | 4388 | 210 | 0.05 | 0.76 | 0.19–2.96 |
| 3 | 17 | 205 996 | 1758 | 83 | 0.04 | 0.75 | 0.18–3.19 |
| Othere | 6 | 43 519 | 353 | 25 | 0.07 | 1.12 | 0.27–4.71 |
| Distancing, ft | |||||||
| 6 | 10 (9%) | 54 557 | 276 | 12 | 0.04 | — | — |
| 3 | 76 (67%) | 610 236 | 4140 | 207 | 0.05 | 1.15 | 0.31–4.24 |
| <3 | 27 (24%) | 278 141 | 2273 | 111 | 0.05 | 1.12 | 0.28–4.45 |
CI, confidence interval; —, reference group for Poisson regression.
This analysis excludes the composite North Carolina charter schools district because of varying practices among schools.
Calculated by the composite number of student within-school–acquired infections (secondary infections) divided by the number of student community-acquired infections (secondary infections) for districts in each category of bus practices or distancing.
Relative rate of secondary transmission for each primary infection, compared with the reference range (for bus analysis: 1 child per seat; for distancing analysis: 6 ft of distancing). Relative rates were calculated by quasi Poisson regression, with the number of primary student cases as the denominator.
Robust CIs were calculated to account for overdispersion.
“Other” category was assigned when districts could not give a policy practice for children per bus seat because of widely varying practices.