Effect of Fall 2020 K-12 instruction types on COVID-19 cases, hospital admissions, and deaths in Illinois counties.

• Illinois counties with more online or hybrid K-12 pupils had fewer new COVID-19 cases. • Illinois counties with more in-person K-12 pupils had more new COVID-19 cases. • New county COVID-19 cases were similar for online and hybrid K-12 instruction types. • New county COVID-19 hospital admissions were similar for all K-12 instruction types. • New county COVID-19 deaths were similar for all K-12 instruction types. One of the most difficult public policy decisions associated with the COVID-19 pandemic has been about how to offer K-12 instruction. We sought to determine whether differences in instruction types at the beginning of the 2020-2021 school year were related to differences in COVID-19 cases, hospitalizations, and deaths in Illinois counties during the first 3 weeks of the school year. We divided Illinois counties into 3 groups based on the instruction type used for a majority of K-12 students at the start of the school year: in-person, hybrid, or online-only. We used synthetic control analysis to match counties between the 3 groups. Both majority hybrid and majority online-only counties had significantly fewer new cases than majority in-person counties. There were no significant differences in new cases between majority hybrid counties and majority online-only counties or in new hospital admissions or deaths between any of the 3 county groups. This paper adds to the growing scientific consensus that at least some forms of in-person K-12 instruction have not contributed significantly to the spread of the pandemic. However, our results suggest that there may be an important difference between fully in-person instruction and hybrid instruction. [ABSTRACT FROM AUTHOR]