WASHINGTON (AP) — President-elect Joe Biden has picked a former Food and Drug commissioner to lead vaccine science in his drive to put 100 million shots into the arms of Americans in his administration’s first 100 days and stem the COVID-19 pandemic. Dr. David Kessler, who will have the title of chief science officer of COVID response, headed the Food and Drug Administration in the 1990s under presidents of both political parties. He has been acting as a top pandemic adviser to Biden and his appointment was announced Friday by the presidential transition office.