Alva Review-Courier -

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. The shift is happening just when millions more Americans are becoming eligible to receive vaccines.

The need to give each person two doses a few weeks apart vastly complicates the country’s biggest-ever vaccination campaign. And persistent uncertainty about future vaccine supplies fuels worries that some people will not be able to get their second shots in time.

In some cases, local health de...