SACRAMENTO (CBS13) — Monday marked the return of an indoor mask mandate at the Sacramento City Unified School District as students begin the last two weeks of the school year.

This move comes after the Centers for Disease Control and Prevention placed Sacramento County last week into the “high” level category of COVID-19 community transmission. Other nearby counties have also been moved into the same tier, including Yolo, Solano, and Placer counties.

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Dr. Dean Blumberg, a pediatric infectious disease expert at UC Davis, says that most new masking requirements will likely be on an “individual level” rather than one of public health. He added that while mask mandates might be returning amid a rising tide of cases, it’s unlikely that there’ll be any COVID-related lockdowns or closures in the near future.

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Last week, Alameda County became the first in California to reinstate indoor masking requirements. Other school systems that have returned to masking are UCLA and Cal Poly San Luis Obispo.

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According to Blumberg, vaccines for children younger than 5 years old are expected to be available later this month. He also anticipates that Americans could get access to improved COVID-19 vaccines in the fall.