“There is increasing data to suggest that schools can safely reopen,” she said, adding that “safe reopening does not suggest that teachers need to be vaccinated in order to reopen safely.”

Walensky’s remarks at a briefing in Washington come as the Biden administration faces pressure to reopen schools, caught between its pledge to safely do so and demands from teachers’ unions about their working environments.

Under guidance provided by the Advisory Committee on Immunization Practices, teachers are considered essential workers, a priority category for immunizations, Walensky said. While teachers are eligible for shots in many parts of the U.S., state criteria vary widely, and vaccine supply remains a significant constraint.

Last week, the CDC released a paper as part of its Morbidity and Mortality Weekly Report focused on reopening schools in a rural Wisconsin county last fall. It found that while 191 Covid-19 cases were confirmed among students and staff, just seven student cases were tied to spread at school.

The report concluded that with precautions such as masking and keeping students in small group cohorts, “transmission risk within schools appeared low, suggesting that schools might be able to safely open with appropriate mitigation efforts in place.”

–With assistance from Josh Wingrove, Jeannie Baumann and Jacquie Lee.