WASHINGTON - Speaking at a White House coronavirus task force briefing on Friday, Dr. Anthony Fauci says scientists are trying to answer the two most pressing questions for millions of Americans already fully vaccinated against COVID-19: Can they become infected without showing any symptoms, and if so, can they transmit the coronavirus to someone else?Fauci said at the White House coronavirus briefing Friday that a large trial is under way involving 12,000 college students at more than 20 universities.RELATED: Boston, Norfolk, Newark: White House COVID-19 task force names 3 cities as mass vaccination centers"This is a question of extreme importance," he said.