Vaccine advisers to the US Food and Drug Administration will meet Friday to discuss whether to recommend Johnson & Johnson’s Covid-19 vaccine for emergency use authorization. The vaccine is the third under consideration for the US market, and would be the first single-dose Covid-19 shot available here. Like the earlier Covid-19 vaccines, it was developed and tested at a remarkable pace, condensing into months what might have taken years before the pandemic.  But there are few answers on what will happen if and when it is authorized. The White House said Monday it has not made any plans yet for distributing the vaccine if it wins authorization. There are vague totals of how many doses will be available immediately and no word on exactly where those doses will go. To read the full story.