Like those in the surging crowd, Caldwell and her parents, both in their late 60s, had heard by word of mouth that extra doses of the Pfizer vaccine had suddenly become available at the hospital — and the doses would expire if they didn’t get into people’s arms that frigid January morning. No one knew how many shots were on hand as they climbed out of cars and buses, forming a line that snaked through the hospital’s parking garage and around the block.

Caldwell’s parents would endure nearly four hours of anxious waiting and confusion before they finally reached the front of the line and received the shots.

“It was like ‘The Hunger Games,’ ” Caldwell said, referring to the post-apocalyptic film in which people fight one another to survive. “It really felt like it was every man and woman for themselves — and only the strongest made it to the end.”