NEW YORK (AP) — COVID-19 vaccines will be shipping in the U.S. after getting emergency authorization, but supplies will be limited for some time. Officials say around 3 million shots will be shipped initially, with allocations based on a state’s population of people 18 and older. The government is holding back enough to ensure people can get a necessary second dose. For now, only Pfizer’s vaccine is being shipped, but other vaccines are making their way through the review process. In December, officials expect to be able to give 20 million first shots. Wide availability is expected by the middle of next year.