WASHINGTON – The head of the agency responsible for approving any COVID-19 vaccine for the U.S. was summoned to the White House Tuesday as an increasingly frustrated President Donald Trump complained approval wasn't coming faster.White House Chief of Staff Mark Meadows called in Stephen Hahn, the head of the Food and Drug Administration, for a meeting as the agency weighed whether to allow emergency use of the first vaccines that could help defeat the coronavirus.Trump has been livid with the FDA for not moving faster on the vaccine, blaming it in part for his reelection loss.