MIAMI — The NBA told its players, coaches and referees on Sunday that they should receive booster shots against the coronavirus, with particular urgency for those who received the single-dose Johnson & Johnson vaccine. The league and the National Basketball Players Association — working jointly based on guidance from the NBA’s public health and infectious disease experts — said those who received Johnson & Johnson shots more than two months ago should get a booster. The booster recommendation also was made for those who received the Pfizer and Moderna vaccine at least six months ago. The league recommendations, which were obtained by The Associated Press, called for those who got Johnson & Johnson vaccines originally to seek a Pfizer or Moderna booster. Those who got Pfizer or Moderna may simply get whatever booster is available, the league said. Data used to make the league’s determinations showed that antibody levels for Pfizer and Moderna recipients wane after six m...