Mixing vaccines? New study could make second doses easier to find

(NBC News) Mass COVID-19 vaccination sites are shifting into high gear.

The Texas Motor Speedway in Fort Worth is one of several now delivering thousands of doses per day.

“It’s military-style precision that we’re operating out here,” said Denton County Judge Andy Eads.

Baseball parks, including New York’s Yankee Stadium, are preparing for clinics of their own, part of a national push to open more super-sites and make good on the Biden administration’s promise to deliver 100 million shots in 100 days.

The U.S. has averaged more than 1.3 million shots per day the past week, and COVID cases overall are declining.

Still, spreading virus variants are threatening that progress, and many patients are having trouble securing a second dose.

A new study in the United Kingdom is looking at the effects of mixing vaccines, with patients receiving different types for first and second doses.