Dr. Anthony Fauci, a key member of the White House’s coronavirus task force, warned senators Tuesday that states and cities face serious consequences if they open up too quickly amid the pandemic.

Fauci urged states not to reopen until they know they have the capabilities to handle an inevitable uptick in cases once they relax stay-at-home orders.

In a high-profile hearing where witnesses and many lawmakers joined via video conference, Fauci also told a Senate committee on Tuesday it was a “bridge too far” for schools to expect a vaccine or widely available treatment for Covid-19 by the time students return to campuses in the fall, though he expressed optimism a vaccine would be developed in the next year or two.

Fauci, who leads the National Institute of Allergy and Infectious Diseases, was subdued but candid in his testimony about efforts to respond to the coronavirus outbreak and roll back stay-at-home orders on Tuesday in the Senate’s first hearing on the coronavirus outbreak since March.

“My concern that if some areas — cities, states or what have you — jump over those various checkpoints and prematurely open up, without having the capability of being able to respond effectively and efficiently, my concern is we will start to see little spikes that might turn into outbreaks,” Fauci said in testimony before the Senate Health, Education, Labor and Pensions Committee.