WASHINGTON (AP) — The U.S. has given the final go-ahead to the nation’s first COVID-19 vaccine, launching emergency vaccinations in a bid to end the pandemic. Shots will begin in a few days after Friday’s decision by the Food and Drug Administration. The FDA called the vaccine from Pfizer and its German partner BioNTech safe and strongly protective. But initial doses are scarce and rationed, with health workers and nursing home residents first in line. Enough for the general population isn’t expected until spring, and experts urge people to mask up and keep their distance during a long, grim winter.