I have no idea if this is the specific clip referred to; but, it's a pretty good one:

https://www.youtube.com/watch?v=nTlxpxdH3Yk

To be reasonably fair to Fauci, he does seem to make it a point to stop just short of claiming 100% effective - in fact, he specifically mentions 95% - but regardless, he repeatedly asserts that if you are vaccinated, you shouldn't worry about getting infected (i.e. you may as well assume 100% effective)... this was over 2 years ago, though; and, I haven't heard anyone making such a ridiculous assertion anytime recently.

I tried watching it and couldn't, as a vaxxed regretful man, I just want to yell at them.