Here is what happened, and this is a quote from the above link:
Throughout 2021, Biden acted as the vaccines' principle cheerleader, urging all eligible Americans to get vaccinated at their earliest opportunity. Although his numerous public statements about the vaccines tended to be, for the most part, reasonably accurate and cogent in terms of reflecting the guidance of the medical community, on at least one occasion Biden grossly overstated the vaccines' efficacy. This occasion is then described:
Biden's impromptu claims about the efficacy of the vaccines were therefore inaccurate, nor did he acknowledge or correct his mistake. He did, however, more accurately state at another point in the same appearance that "If you're vaccinated, even if you do 'catch the virus,' quote, unquote, like people talk about it in normal terms, you're -- not many people do. If you do, you're not likely to get sick. You're probably going to be symptomless. You're not going to be in a position where your life is in danger.
Context is all, and if in a history of getting it right and saying the vaccination is not a 'cure-all', probably 100's of times. Biden once gets it wrong and remember he is a man prone to verbal gaffes, you really need to be very prejudiced or very gullable to believe this one gaffe represents anything but what it is - a gaffe - As someone also prone to getting words and ideas garbled at times, he has my sympathy.