But 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... Health officials in a number of other states presented a similarly discouraging picture. The pause on the Johnson & Johnson vaccine, they said, effectively kicked it aside for good; only about 3.5 million doses have been used since the pause was lifted on April 23. Kim Deti, a spokeswoman for the Wyoming Health Department, said the graph of uptake in her state told the vaccine’s story: a significant climb in the early weeks of its rollout, followed by a plateau that began around the pause. State officials had initially hoped the Johnson & Johnson shot would be a workhorse: a versatile, easy-to-store tool they could stockpile at mass vaccination sites, quickly reaching thousands of people they would not need to track down for a second dose. But after demand dropped, their goals grew more modest... Between the small number of doses distributed and the lack of interest in them, public health experts say, the United States missed a critical opportunity to address health disparities with a vaccine that should have been ideal for reaching vulnerable populations.