Rochelle Walensky, the new director of the Centers for Disease Control and Prevention, reiterated Sunday that her agency doesn't believe all teachers must receive COVID-19 vaccinations before they return to classrooms for in-person learning.

"I'm a strong advocate of teachers receiving their vaccinations, but we don't believe it's a prerequisite for reopening schools," Walensky said Sunday during an appearance on CNN's "State of the Union."

The CDC last week issued guidance for school reopenings that likewise said that teacher vaccinations weren't imperative for the reopening of school buildings to students and teachers. Instead, the guidance said that other methods at curbing the spread, like mask-wearing and social distancing, were more important to get kids and teachers back in classrooms safely.

The guidance also notes that the precautions schools should take depends on the state of COVID-19 in their communities. Schools in regions with high levels of virus transmission should require mask-wearing and physical distancing, the CDC said.

Walensky also Sunday said she believed that teachers at higher risk of suffering serious COVID-19 side effects should continue to opt for virtual learning over in-person instruction.

"We have in the guidance clear language that specifies that teachers that are at higher risk...teachers and students that are higher risk, and their families, should have options for virtual activities, virtual learning, virtual teaching," she added.

The question of when and how schools should safely open to students has been the subject of debate since school systems across the US closed their doors to students last spring, sending students to online classrooms to prevent the spread of the virus.

But nearly a year later, schools across the US have taken different approaches, as some have returned to in-person instructions, while others keep students at home with either entirely virtual learning or a hybrid approach. About 60% of schools in the US have reopened some classrooms in some capacity, according to CDC data.

"In-person learning has not been associated with substantial COVID-19 transmission," Walkensky said last week.

Schools in New York City and in Chicago, two of the three largest school districts in the US, last week made steps to reopen some classrooms to students after months-long shutdowns kept most students in virtual learning environments.

Walensky noted Sunday that teachers are among some of the first people the CDC recommends be vaccinated, which includes other frontline workers and people over the age of 75.