evidence: FDA panel backs Moderna COVID booster shot for high-risk Americans, clearing the way for a 3rd jab A key federal advisory committee voted unanimously Thursday to recommend emergency authorization of a booster shot for older and more vulnerable recipients of Moderna’s COVID-19 vaccine, a sign that millions of Americans who received their second Moderna dose at least six months ago will likely be cleared for a third jab as soon as next weekend. [...] "Some real-world effectiveness studies have suggested declining efficacy of Moderna COVID-19 vaccine over time against symptomatic infection or against the Delta variant, while others have not," the FDA scientists said in the briefing document.