A student is seen walking down the steps of PS 139 closed public school in the Ditmas Park neighborhood of Brooklyn, New York, United States on October 8, 2020.

Michael Nagle | Xinhua News Agency | Getty Images

School teachers and staff could play a “central role” in the transmission of Covid-19 in schools that fail to follow social precautions and precautions against facial covering. Vaccination for the disease could help get students back to class safely, according to a new state study released Monday.

The U.S. Centers for Disease Control and Prevention studied the spread of the coronavirus in eight Georgia public elementary schools in the same school district between December 1 and January 22, including 24 days of face-to-face study. During that period, the average number of cases per 100,000 residents of the county rose by almost 300%, the study said.

The Federal Health Office, together with the state and local health authorities, found nine Covid-19 “clusters” in which 13 educators and 32 pupils at six of the eight primary schools were involved.

The median cluster size – defined as three or more linked Covid-19 cases – was six people, and one educator was the “index patient” or the first case identified in four of these clusters, the CDC found. One student was the first patient in a cluster while the other four clusters had an unidentifiable index patient.

All but one of the clusters included “at least one educator and a likely educator-to-student transfer,” according to the study.

“Educators played an important role in spreading Covid-19 in schools. The spread of Covid-19 often occurred at face-to-face meetings or lunches and then spread to classrooms,” CDC Director Rochelle Walensky told reporters at a briefing on late monday. “The two main reasons for the spread of Covid-19 in these schools were inadequate physical distancing and mask adhesion in schools.”

She said students couldn’t practice social distancing because classes were too full and desks weren’t at least three feet apart.

In the study, CDC researchers said they conducted interviews with parents, educators, and school principals and examined seating plans, classroom layouts, physical distancing, and adherence to recommended mask use in face-to-face learning to identify case links.

They found that social distancing recommendations were “less than ideal” followed across all nine clusters. Students sat less than three feet apart and in many cases the spread of the virus could have spread among students in small group sessions, according to the study.

The results come just over a week after the CDC unveiled new guidance on how to safely reopen schools to face-to-face learning despite the spread of the virus. Among the numerous recommendations, the CDC advises districts to introduce their reopening plans according to the severity of the outbreak in their areas.

It also states that schools should adopt “essential elements” for resumption of personal learning, including wearing masks, physical distancing, and monitoring the level of spread in the surrounding community.

While the CDC advised states to give priority to vaccinating teachers and staff “as soon as supplies permit,” the guidelines did not recommend it for reopening. However, the study, published Monday, suggested that vaccinating educators could be important in protecting the most vulnerable while reducing disruptions to personal learning and potentially preventing the virus from spreading in schools.

“While COVID-19 vaccination is not required for schools to reopen, it should be viewed as an additional mitigation measure that should be added as it becomes available,” the researchers wrote.

– CNBC’s Will Feuer contributed to this report.