Dr Anthony Fauci, one of the U.S. President's top advisors on the coronavirus pandemic, says "there's no guarantee" of finding a safe and effective vaccine.
But, in his testimony to the Senate Health Committee on Tuesday, Dr Fauci also said vaccines currently under development are showing promising signs.
CLIP: Dr Anthony Fauci
IN: "We are cautiously..."
OUT: "...to pursue this."
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