CHICAGO : The United States may not need Oxford-AstraZeneca's COVID-19 vaccine, even if it wins U.S. regulatory approval, Anthony Fauci, the nation's top infectious disease doctor told Reuters on Thursday.The vaccine, once hailed as another milestone in the fight against the COVID-19 pandemic, has been dogged by questions since late last year, even as it has been authorized for use by dozens of countries, not including United States.Fauci, director of the National Institute of Allergy and Infectious Diseases and chief medical adviser to the White House, said the United States has enough contracts with other vaccine makers to vaccinate its entire population, and possibly enough for booster shots in the fall.Asked whether the United States.