On Friday, Centers for Disease Control and Prevention Director Dr. Rochelle Walensky said the agency would release guidance on school reopenings sometime next week.
Dr. Walensky told reporters that "schools should be the last places closed and the first places opened," according to NPR.
In an article last week in the Journal of the American Medical Association, CDC scientists published an article that stated some schools could reopen safely by following safety precautions.
However, the report included a disclaimer that the conclusions "do not necessarily represent the official position" of the CDC.
The school reopening debate is presenting an early test of President Joe Biden's allegiance with powerful teachers' unions.
As teachers' unions in some areas demand vaccines before returning to in-person instruction, the CDC's director on Wednesday said teachers do not need vaccines to reopen safely.
Some believed the CDC's position would drive a wedge between Biden and teachers' unions, but unions say that's not the case.
Even those demanding vaccines say shots would not be required if schools were taking other steps to make buildings safe.
But they say schools have failed to update ventilation systems and take other important steps, making vaccines critical.