Here is the relevant excerpt from the attached Politico article on that issue...

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"I will say that I do not trust Donald Trump" on the reliability of a vaccine, Harris said. The California Senator, however, added that she would trust a "credible" source who could vouch that a vaccine was safe for Americans to receive.
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That credible source was Dr. Fauci, about whom DJT voiced several criticisms, based on Fauci's refusal to go along with Trump's desire to "Downplay" COVID-19 in advance of the 2020 elections. Remember that later on Biden/Harris made Dr. Fauci their Chief Medical Advisor on COVID-19 pandemic response.

Next time, do some Critical Thinking and research prior to posting...or just stick to Quips...

Link: https://www.politico.com/news/2020/09/05/kamala-harris-trump-coronavirus-vaccine-409320