In a Jan. 21, 2021, file photo, people who had appointments to get COVID-19 vaccinations talk to New York City health care workers outside a closed vaccine hub in the Brooklyn borough of New York after they were told to come back in a week due to a shortage of vaccines. 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)