Table 3.

The minimum non-pharmaceutical intervention(s), or minimum within-school vaccination coverage of the eligible population, needed to reduce the risk of symptomatic infection to beneath a given risk level (e.g., 50 cases per 1,000 population), assuming that 70% of the fall 2021 vaccine-eligible (12+) community has received a vaccine at 85% effectiveness. ‘Not observed’ indicates that no combination of interventions examined in this study reduced excess risk beneath the indicated threshold. Masks refers to universal masking regardless of vaccination status.

		Population-wide risk tolerance — symptomatic cases per 1,000 population			School-based risk tolerance — < 2 cases per school*
		<50	<25	<10
Students	Elementary school – half susceptibility	Masks	Masks + testing	Masks + cohorts	Masks + cohorts
	Elementary school – equal susceptibility	Masks + cohorts	Masks + cohorts	Not observed⁎⁎	Not observed⁎⁎
	Middle school	Masks or 95% coverage	Masks + testing	Masks + cohorts	Not observed⁎⁎
	High school	Masks or 80% coverage	Masks	Masks + testing	Masks + cohorts
Teachers/staff	Elementary school – half susceptibility	Masks or 80% coverage	Masks + testing	Masks + cohorts
	Elementary school – equal susceptibility	Masks + testing	Masks + cohorts	Not observed⁎⁎
	Middle school	Masks or 90% coverage	Masks + testing	Masks + cohorts
	High school	Masks or 80% coverage	Masks or 95% coverage	Masks + testing

^⁎Assuming a 380-person elementary school, 420-person middle school, and 680-person high school.

^⁎⁎Not observed under the interventions examined here.