No specific safety concerns'US President Donald Trump signed an executive order "to ensure that American citizens have first priority to receive American vaccines."But he faces questions over whether the White House missed an opportunity to shore up sufficient doses in the months ahead.President-elect Biden warned, meanwhile, that coronavirus vaccination efforts in the United States will "slow and stall" if Congress does not urgently come up with funding.He stressed it was imperative for lawmakers to "finish the bipartisan work underway now or millions of Americans may wait months longer to get the vaccine."Biden also pledged that his administration would carry out at least 100 million vaccinations in his first 100 days in office, a more.