He urged areas with high rates of cases to "think twice" before reopening schools, adding it's not "all or nothing" and schools may have to adjust and take precautions such as wearing masks, having classes outside or having hybrid learning environments.
RELATED: NYC schools not ready to reopen, teachers' union says
Fauci also criticized the federal coronavirus response saying that he would "like to see a consistent message for school reopening" from the federal government to guide the local authorities.
He stressed that children "can transmit to adults just as easily as adults can transmit to adults."
Even though children have lower chances of "having a serious outcome" Fauci said that some children do get seriously ill.
RELATED: Back to school information
He said colleges and universities face different challenges in large part because there are students "coming from all over the country" with the potential to spread the virus on college campuses.
Fauci said it "is conceivable" that universities could bring students back safely, stipulating that the campuses would have to have the resources to do things like testing every students before they arrive, screening individuals and having empty dorms to safely isolate students if they become infected.
When asked when a vaccine might be available, Fauci said that based on the ongoing trials, he believes that we will know around "the end of this calendar year and maybe into the end of 2021 whether or not we have a safe and effective candidate."
WATCH: New York Governor Cuomo said the flu and COVID-19 will stress the state's testing capacity
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