Could a vaccine change market leadership? When will enough doses of FDA-approved Covid-19 vaccine(s) to inoculate 25 million people be distributed in the US? The superforecasters of the Good Judgement Project believe there is a 93% probability we will have an FDA-approved vaccine in a year, and enough of it to inoculate 25 million people in the US. This is up from just 20% in the dark days of April.