The Delta Variant Now Makes Up More Than 50% Of COVID-19 Cases In The US

The Centers for Disease Control and Prevention officials reported Tuesday that the delta variant made up more than 50% of COVID-19 cases in the U.S. between June 20 and July 3 — up 30.4 from the previous two-week period. What is the latest news and research about variants of SARS-CoV-2 and vaccine effectiveness? How worried should we be?