An unvaccinated primary school teacher in Marin County, California spread COVID-19 to 26 other people, including 50% of her classroom, after spending two days sick with the coronavirus at school while not always being masked, according to a new Centers for Disease Control and Prevention report.

Friday’s report highlights the importance of vaccinating and masking elementary school teachers in order to protect children younger than 12 years old who are not yet vaccinated.

“We know how we can protect our children in school. “We have the tools,” Rochelle Walensky, Director of CDC, said Friday as she discussed the report at a White House COVID-19 briefing.

Walensky stated that the teacher was both unvaccinated and symptomatic. She also “wasn’t afraid to read aloud to her class” where her students were too young to need vaccinations.

Her actions led to 12 COVID-19 cases in the class of 24 children, six other illnesses at K-8 school and eight infected parents and siblings.

To determine if the cases were related, the investigation used viral genome sequencing. The Delta variant of COVID-19, which is twice as contagious than other viruses, was identified in all COVID-19 cases.

Nobody was admitted.

The CDC created a map of each classroom to give a better understanding of how the virus circulated and the preventive measures taken.

To promote ventilation and good spacing, students’ desks were placed six feet apart. Windows and doors were left unclosed to allow for airflow. An air filter was also installed at the head. According to interviews conducted by the CDC with parents, kids adhered to CDC guidelines regarding masking and distancing at school.

But, with an unmasked and unvaccinated teacher at its helm, all that didn’t matter.

While she was symptomatic, she continued to teach for two days, beginning May 19. Her symptoms began on May 19, when her initial congestion and fatigue, which she thought were allergies, became a fever, headache, and cough.

It did seem, however, that sitting further away from the sick teacher helped protect students, which makes sense when you consider how the coronavirus travels from person to person through the air when sick people talk or shout.

According to the CDC report, “The attack rate in two rows closest to the teacher’s desk was 80% (8 out of 10) and 21% (3 out of 14) in three back rows.”

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This finding confirms what other experts have said for some time: more adults must be vaccinated to prevent the Delta variant.

Mike Osterholm, Director of the Center for Infectious Disease Research and Policy, University of Minnesota, said that 6 feet is not magic. He stressed that he doesn’t believe the CDC guidelines are sufficient to stop the spread of the more contagious Delta variant.

Osterholm stated, “We can make [school] more safe.” “We use our vaccines first.”