Abstract
In September of 2020, the Iowa Department of Public Health released guidance stating that persons exposed to someone with coronavirus disease (COVID-19) need not quarantine if the case-patient and the contact wore face masks at the time of exposure. This guidance differed from that issued by the Centers for Disease Control and Prevention. To determine the best action, we matched exposure information from COVID-19 case investigations with reported test results and calculated the secondary attack rates (SARs) after masked and unmasked exposures. Mask use by both parties reduced the SAR by half, from 25.6% to 12.5%. Longer exposure duration significantly increased SARs. Masks significantly reduced virus transmission when worn by both the case-patient and the contact, but SARs for each group were higher than anticipated. This finding suggests that quarantine after COVID-19 exposure is beneficial even if parties wore masks.
Highlights
In September of 2020, the Iowa Department of Public Health released guidance stating that persons exposed to someone with coronavirus disease (COVID-19) need not quarantine if the case-patient and the contact wore face masks at the time of exposure
The Iowa Department of Public Health (IDPH) change in guidance provided an opportunity to lessen the burden of the pandemic on Johnson County, we were concerned about a potential increase in transmission rates
Because data supporting this change in guidance were lacking, we designed a prospective cohort study to evaluate the potential risk for increased virus transmission by measuring the secondary attack rates (SARs) of COVID-19 between persons exposed when both parties were masked and those exposed when >1 person was unmasked
Summary
The IDPH change in guidance provided an opportunity to lessen the burden of the pandemic on Johnson County, we were concerned about a potential increase in transmission rates Because data supporting this change in guidance were lacking, we designed a prospective cohort study to evaluate the potential risk for increased virus transmission by measuring the secondary attack rates (SARs) of COVID-19 between persons exposed when both parties were masked and those exposed when >1 person was unmasked. While examining the available data, we identified several additional risk factors of interest, including symptom status, exposure setting, and exposure duration This information enabled us to examine additional guidance relating to COVID-19, such as early release from quarantine and the potential for airborne transmission, to ensure that our recommendations did not increase the risk for transmission in the community
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