The first US coronavirus vaccinations outside of clinical trials initiated on Monday, launching the most crucial mass immunization campaign since polio shots were distributed in the 1950s.A nurse in New York was among the first to take the shot, and health workers throughout the US were also set to receive the freshly authorized vaccine produced by Pfizer Inc and BioNTech SE. Pfizer shipped vaccine vials out on Sunday, and hospitals and healthcare centers across the country received them early Monday.A total of 55 sites Nationwide had acquired vaccine shipments by roughly noon on Monday, according to Gen. Gustave Perna, chief operation officer for Operation Warp Speed, the US government’s coronavirus response program. He stated at a news conference that plans remain on target of a total of 636 locations to acquire vaccines by Wednesday and an additional 581 between Thursday and Sunday, completing distribution of an initial 2.9 million doses. The vaccines are given in two doses several weeks apart. The government has a reserve of 500,000 doses in case any issues arise, he added.