The outbreak location was an elementary school in Marin County, California, which serves 205 students in prekindergarten through eighth grade and has 24 staff members. In addition to vaccination for eligible persons, strict adherence to nonpharmaceutical prevention strategies, including masking, routine testing, facility ventilation, and staying home when symptomatic, are important to ensure safe in-person learning in schools ( 3). Vaccines are effective against the Delta variant ( 2), but risk of transmission remains elevated among unvaccinated persons in schools without strict adherence to prevention strategies. WGS of all 18 available specimens identified the B.1.617.2 (Delta) variant. Among the 27 total cases, 22 (81%) persons reported symptoms the most frequently reported symptoms were fever (41%), cough (33%), headache (26%), and sore throat (26%). Among these additional cases, three were in persons fully vaccinated in accordance with CDC recommendations ( 1). Eight additional cases were also identified, all in parents and siblings of students in these two grades. During May 24вЂ“June 1, six of 18 students in a separate grade at the school, all also too young for vaccination, received positive SARS-CoV-2 test results. The attack rate in the two rows seated closest to the teacherвЂ™s desk was 80% (eight of 10) and was 28% (four of 14) in the three back rows (FisherвЂ™s exact test p = 0.036).

During May 23вЂ“26, among the teacherвЂ™s 24 students, 22 students, all ineligible for vaccination because of age, received testing for SARS-CoV-2 12 received positive test results. A total of 27 cases were identified, including that of the teacher. To characterize the outbreak, on May 26, MCPH initiated case investigation and contact tracing that included whole genome sequencing (WGS) of available specimens. Beginning May 23, additional cases of COVID-19 were reported among other staff members, students, parents, and siblings connected to the school. On occasion during this time, the teacher read aloud unmasked to the class despite school requirements to mask while indoors. The teacher reported becoming symptomatic on May 19, but continued to work for 2 days before receiving a test on May 21. On May 25, 2021, the Marin County Department of Public Health (MCPH) was notified by an elementary school that on May 23, an unvaccinated teacher had reported receiving a positive test result for SARS-CoV-2, the virus that causes COVID-19.

School mate 2 broken animtion