TABLE 2.
Quasi-Poisson Regression of Predicted Secondary Cases and Relative Rate of Secondary Transmission by Masking Policy
| Masking Policy | Districts, n (%) | Students and Staff, n | Total Primary Infections, n | Total Secondary Infections, n | Predicted Secondary Cases per 100 Primary Cases | 95% CI | Relative Rate of Secondary Transmission | 95% CI |
|---|---|---|---|---|---|---|---|---|
| Universal | 46 | 1 227 131 | 38 200 | 2776 | 7.3 | 6.3–8.4 | — | — |
| Partiala | 9 | 38 261 | 2106 | 231 | 11.0 | 6.5–18.4 | 1.5 | 0.88–2.59 |
| Optional | 6 | 4576 | 295 | 78 | 26.4 | 10.9–64.4 | 3.6 | 1.47–8.98 |
CI, confidence interval; —, reference group for regression analysis.
a
Partial masking districts included: 4 districts that initially had optional masking and transitioned to masks required, 2 districts that transitioned between mask optional and required more than once during the study period, and 3 districts that had required and optional masking varying by either school grade level, or by community transmission threshold.