Coronavirus And Variants Vs. Vaccine: Our Behavior Could Determine The Winner

As of Thursday, 99.6 million U.S. residents have received at least one dose of a COVID-19 vaccine, according to the Centers for Disease Control and Prevention, and more than 56 million people have been fully vaccinated.

Just as impressive? Nearly 3.4 million doses were delivered in a single day Thursday.

The CDC also released new guidelines that say people who have been fully vaccinated can travel with "low risk" but should still take precautions. Fully vaccinated people do not need to get a COVID-19 test before or after travel and do not need to self-quarantine after travel, the guidance says.

But there's still plenty to worry about — 32 states are showing increases in new infections. Among them, cases in Michigan have gone up 107%, and researchers say they've discovered that state's first case of the highly contagious Brazil variant there.

Host Peter O'Dowd talks to Dr. Jeanne Marrazzo, head of the Division of Infectious Disease at the University of Alabama at Birmingham.