In a Jan. 24, 2021, file photo, people work near refrigerators used to store the Pfizer vaccine for COVID-19, as patients who have received the shot sit in an observation area during a one-day vaccination clinic set up in an Amazon.com facility in Seattle and operated by Virginia Mason Franciscan Health. 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/Ted S. Warren)