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Volume 28, Number 1—January 2022
Mask Effectiveness for Preventing Secondary Cases of COVID-19, Johnson County, Iowa, USA
|Mask use, case-patient/contact||Negative||Positive||Secondary attack rate (95% CI), %|
||20.5 (18.1– 23.2)
|Total unmasked*||439||151||25.6 (22.3–29.4)|
|Unmasked/unmasked||364||131||26.4 (22.9– 30.7)|
|Unmasked/masked||36||4||10.0 (4.0– 25.3)|
|School-age, 5–18 y|
*When >1 person was unmasked during exposure.
Page created: October 12, 2021
Page updated: October 12, 2021
Page reviewed: October 12, 2021
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