US vaccine drive complicated by 1st, 2nd dose juggling act

FILE - In this Jan. 27, 2021, file photo, woman asks directions at the entrance to Vista View Park where a COVID-19 vaccination site has opened for second doses in Davie, Fla. As health officials race to vaccinate people across the U.S., the need to give each person two doses a few weeks apart is adding a layer of complexity to the country’s biggest-ever vaccination campaign. (Joe Cavaretta/South Florida Sun-Sentinel via AP, File)

The U.S. has entered a tricky phase of the COVID-19 vaccination effort as providers try to ramp up the number of people getting first shots while also ensuring a growing number of others get second doses just when millions more Americans are becoming eligible to receive vaccines.