Bill Oxford/iStock(NEW YORK) For Mitchell Kronenberg, answers on the Johnson & Johnson vaccine can't come soon enough. A 42-year-old dad living outside Charlotte, North Carolina, Kronenberg enrolled in a clinical trial for the single-dose vaccine and got his shot last January. Since then, he's been patiently waiting for U.S. federal regulators to tell him what to do next to stay safe: Should he get another Johnson & Johnson shot? Switch to Moderna or Pfizer? Is his single-shot vaccination enough to protect him from spreading the virus to his unvaccinated 4-year-old son? "Why is it taking so long? You have people out on a ledge out here," he said of the process. The U.S. Food and Drug Administration is expected to decide as early as Wednesday whether the 15 million Americans who got the single-dose J&J shot by Janssen Pharmaceutical Companies should get a second dose. The decision comes after studies suggested effectiveness against moderate and severe