Production problems and a brief pause on its use kept the one-dose vaccine from becoming the game changer that health officials across the country believed it would be. … with only 11.8 million doses administered in the United States so far — less than 4 percent of the total — the “one and done” vaccine has fallen flat. States have warned for weeks that they may not find recipients for millions of doses that will soon expire, partly because the vaccine’s appeal dropped after it was linked to a rare but serious blood-clotting disorder and injections were paused for 10 days in April.