Spread in US schools

USA, Teacher learned she was positive 2 days later

Marin County, California, May 19, under 12s

One teacher, not vaccinated, feeling fatigued with some nasal congestion

Worked on, toot of mask for class reading

Air filter, windows open on two walls

6 feet between desks

Learned she was positive two days later

12 of 24 had been infected

6 symptomatic, 6 asymptomatic

Mostly in the two rows closest to her desk

Outbreak spread to other classes

Siblings and parents, including some who were fully vaccinated

Tracy Lam-Hine, epidemiologist for the county

everyone lets their guard down — but the thing is delta takes advantage of slippage from any kind of protective measures

Children under 12, ineligible for vaccines

COVID-19 Projections for K12 Schools in Fall 2021: Significant Transmission without Interventions

Without testing and masking R0 = 4.0

More than 75% of susceptible students get infected within three

months in all settings

With masks, R0 = 2.0

The proportion infected drops to approximately 50%

Testing further drops infections

High, 22%

Mid, 16%

Low, 13%

Conclusion

Without interventions in place, the vast majority of susceptible students will become infected through the semester.

Universal masking can reduce student infections by 26-78%, and biweekly testing along with masking reduces infections by another 50%.

To prevent new infections in the community, limit school absences, and maintain in-person learning, interventions such as masking and testing must be implemented widely, especially among elementary school settings in which children are not yet eligible for the vaccine.

Canada

NZ

Australia

UK data