■ A study found that teachers are key to COVID-19 transmission in schools.

Study shows adults, not students, likeliest to transmit COVID

ATLANTA — A new study finds that teachers may be more important drivers of COVID-19 transmission in schools than students.

The paper released Monday by the U.S. Centers for Disease Control and Prevention studies nine COVID-19 transmission clusters in elementary schools in the Atlanta suburb of Marietta in December and January. That included one cluster where 16 teachers, students and relatives of students at home were infected.

In only one of the nine clusters was a student clearly the first documented case, while a teacher was the first documented case in four clusters. In another four, the first case was unclear. Of the nine clusters, eight involved probable teacher-to-student transmission. Two clusters saw teachers infect each other during in-person meetings or lunches, with a teacher then infecting other students.

“Educators were central to inschool transmission networks,” the authors wrote.

The findings line up with studies from the United Kingdom that found teacher-to-teacher was the most common type of school transmission there, and a German study that found in-school transmission rates were three times higher when the first documented case was a teacher. In some American districts, schools have had to go all-virtual because so many teachers have been exposed to the virus.

Other research has suggested that there’s low transmission of viruses in schools and that they should reopen for in-person instruction, a message that President Joe Biden’s administration has been pushing in recent weeks to mixed success. The 8,700-student Marietta district, like all but a handful in Georgia, has been offering in-person classes since the fall. Superintendent Grant Rivera said more than 90 person of elementary students came back in person.

All the Marietta clusters also involved “less than ideal physical distancing,” with students often less than 3 feet apart, although plastic dividers were placed on desks.

“Physical distancing of greater than 6 feet was not possible because of the high number of in-person students and classroom layouts,” the authors wrote.

In seven cases, transmission may have taken place during small-group instruction sessions where teachers were close to students. Although the authors said they observed students wearing masks, interviews found that “inadequate mask use” by students could have contributed to the spread of infection in five clusters. In other developments:

■ Drugmaker Johnson & Johnson said it will be able to provide 20 million U.S. doses of its single-shot COVID-19 vaccine by the end of March, assuming it gets the greenlight from federal regulators.

■ Gov. Gavin Newsom said more vaccines are headed to California’s vast Central Valley, an agricultural region that’s been hit hard by coronavirus. In the small farming city of Arvin on Monday, Newsom said that 11 mobile clinics will open in the region later this week.

■ Seattle Public Schools is delaying a return to the classroom for its youngest students during the coronavirus pandemic by at least a week because it has yet to reach an agreement with the teachers’ union.

■ Authorities in Houston are opening a giant vaccination center that will serve an estimated 126,000 people over the next three weeks.