A White House official confirmed Thursday that the Biden administration is planning to send 2.5 million doses to Mexico and 1.5 million to Canada as a “loan.”The AstraZeneca vaccine has not been authorized for use in the U.S. but has been by the World Health Organization. Tens of millions of doses have been stockpiled in the U.S. should it receive emergency use authorization, sparking an international outcry that lifesaving doses could not be used overseas.