The coronavirus vaccine developed by AstraZeneca and the University of Oxford provided strong protection against Covid-19 in a large clinical trial in the United States, offering complete protection against the worst outcomes from the disease while causing no serious side effects, according to data released on Monday. The findings, announced in a news release from AstraZeneca, may help shore up global confidence in the vaccine. But the fresh data may not make a difference in the United States, where the vaccine is not yet authorized and may not be needed. If AstraZeneca wins authorization for emergency use in the U.S. based on the new results, the vaccine will likely not become available until May, when federal officials predict that three other authorized vaccine manufacturers will be producing enough doses for all the nation’s adults. The announcement comes at a deeply fraught moment for AstraZeneca. More than a dozen countries […]