Students and teachers vaccinated against Covid-19 will not need to wear masks in US classrooms when school resumes in the fall, health authorities said on Friday (July 9).

The new guidance follows the recent federal approval of the Pfizer-BioNTech Covid-19 shot for Americans aged 12 to 15, with hospitalizations and deaths down sharply since January - but cases beginning an upward trajectory due to the surging Delta variant of the coronavirus.

"Indoors: Mask use is recommended for people who are not fully vaccinated, including students, teachers, and staff," the nation's lead federal public health agency announced in its updated guidance.

Meanwhile, Schools are free to follow the guidelines or ignore them, as per CDC.

"Based on the needs of the community, school administrators may opt to make mask use universally required (ie, required regardless of vaccination status) in the school," the agency says.

The CDC also said that all kindergarten through grade 12 schools in the United States should continue to mandate wearing masks indoors by all individuals who are not fully vaccinated.

Health officials stress that returning to in-person learning in the fall is a "priority."