The Delta variant of COVID-19 continues to spread through the U.S., with Missouri and Kansas seeing high transmission as vaccination efforts remain sluggish in some parts of the country. … On May 22, the variant accounted for only about 2.7% of cases, but as of last week it is now closer to 10% of all cases in the U.S., according to the CDC. However, the rate was already higher in some parts of the country with Missouri recording the variant as roughly 6.8% of cases in the state as of May 22.