TABLE 2. COVID-19 incidence* and rate ratios in 123 elementary schools,† by type of ventilation improvement as a COVID-19 prevention strategy — Georgia, November 16–December 11, 2020.
| Ventilation improvement | No. (%) of schools | No. of enrolled students | No. of cases§ | Cases per 500 students enrolled (95% CI) | RR¶ (95% CI) |
|---|---|---|---|---|---|
|
Total
|
123 (100)
|
66,499
|
417
|
3.13 (2.84–3.44)
|
—
|
| None** |
37 (30.1) |
21,844 |
183 |
4.19 (3.63–4.84) |
Ref |
| Dilution only†† |
39 (31.7) |
21,562 |
127 |
2.94 (2.48–3.50) |
0.65 (0.43–0.98) |
| Filtration ± purification only§§ |
16 (13.0) |
9,133 |
45 |
2.46 (1.84–3.29) |
0.69 (0.40–1.21) |
| Dilution and filtration ± purification¶¶ | 31 (25.2) | 13,960 | 62 | 2.22 (1.73–2.84) | 0.52 (0.32–0.83) |
Abbreviations: CI = confidence interval; GDPH = Georgia Department of Public Health; HEPA = high-efficiency particulate absorbing; RR = rate ratio; UVGI = ultraviolet germicidal irradiation; ± = with or without.
* Case incidence in schools was calculated as the sum of cases reported to GDPH during November 16–December 11, 2020, divided by the number of students enrolled multiplied by 500.
† Excludes schools from the original 169 that reported “Don’t know” to improving ventilation (n = 45) and one school that reported only using an air purification strategy.
§ Number includes both students and staff members with a case of COVID-19 during the study period.
¶ Adjusted for county-level 7-day case incidence per 100,000 population on December 1, 2020.
** Includes schools that reported “No” to improving ventilation and six schools that reported decreasing room occupancy as the only ventilation improvement.
†† Opening doors, opening windows, or using fans.
§§ Using HEPA filters with or without using UVGI and not opening doors, opening windows, or using fans.
¶¶ Opening doors, opening windows, or using fans, and using HEPA filters with or without using UVGI.