In a Jan. 21, 2021, file photo, a man who came to get a COVID-19 vaccine holds his paperwork as he talks to a New York City health department worker outside a closed vaccine hub in the Brooklyn borough of New York. An increasing number of COVID-19 vaccination sites around the U.S. are canceling appointments because of vaccine shortages in a rollout so rife with confusion and unexplained bottlenecks. (AP Photo/Kathy Willens, File)