More than half of U.S. adults have been fully vaccinated, and case rates are at their lowest point since the pandemic began. But there are still a lot of unanswered questions about the future of the pandemic. Questions about variants, vaccine booster shots and the idea of vaccine mandates in schools or publicly-funded universities. We had a chance to put some of the questions — including ones from you — to the nation's top doctor, U.S. Surgeon General Dr. Vivek Murthy, in an interview conducted on Twitter Spaces, a new platform for live audio conversations on Twitter. To participate in future Twitter Spaces conversations, follow us on Twitter @nprAudie and @npratc. You can find our episodes on Twitter and Facebook using the hashtag #NPRConsiderThis.In participating regions, you'll also hear a local news segment that will help you make sense of what's going on in your community.Email us at considerthis@npr.org.