The number 50 was mentioned in passing, but it doesn't sound like he was predicting any specific efficacy number, only that it would not be as high as the rosy 90%+ that was shown by some data. To me, parsing these words is a little nit-picky, since we are talking about a 2 year period during which multiple new and unexpected strains have become dominant, and vast amounts of new clinical data have been published.
And it's true that the quotes come from early on in the pandemic.
However, the claim that it was randos on Twitter and not the experts - at any time - who purveyed the idea that the Covid vaccines would significantly prevent transmission - unlike flu vaccines - is contradicted by the quote from Fauci that I posted in response to the question: "who sold these ideas to the public?"
The parent comment asked "who sold these ideas [that vaccines prevent transmission] to the general public?" From the quote I posted, it certainly seems like Fauci did.
Is there something I'm missing here?