The little purple-capped vials officially arrived at 7:07 a.m. Monday via Priority Overnight in a nondescript white box, the only parcel in the back of the FedEx van idling by the loading docks of Rhode Island Hospital. Martha Roberts, the pharmacy department coordinator for Lifespan, got the alert that the COVID-19 vaccines had arrived — three hours early, in fact — and rushed down with some colleagues to meet them. “Do you know what you’re transporting today?” Roberts asked the delivery man. He sure did: The Pfizer-BioNTech COVID vaccine arrived Monday morning at Rhode Island Hospital, set to go into arms of high-risk health-care workers and hospital staff within a few hours. (They’ll need a second shot in three weeks.)