evidence: - The CEOs of Moderna and Pfizer are now acknowledging that their two-dose vaccines likely will require a third shot, with Moderna CEO Stephane Bancel saying Saturday that the company's two-shot vaccine will probably require a third "booster shot," but that it's not clear how long after the first two shots that will be, and that '"the variant is going to be the big question in terms of boosting." On Thursday, Pfizer CEO Albert Bourla said, "There will be likely a need for a third dose, somewhere between six and 12 months. And then from there, there will be an annual revaccination. But all of that needs to be confirmed." Read more at Fox News and CBS News.