1,000 US counties still have vaccination rates below 30% - particularly in the Southeast and Midwest, CDC says

• 1,000 US counties have vaccination rates below 30%, CDC Director Rochelle Walensky said Thursday.
• Coronavirus transmission will likely increase in these areas as the Delta variant keeps spreading.
• But the US is struggling to put shots in arms: Vaccination rates fell 85% in the last three months.

Nearly half the US population is fully vaccinated, but rates still vary widely from state to state - and even more widely county by county.

Around 1,000 US counties currently have vaccination rates below 30%, Rochelle Walensky, director of the Centers for Disease Control and Prevention, said at a White House press briefing on Thursday.

"These communities, primarily in the Southeast and Midwest, are our most vulnerable," Walensky said. "In some of these areas, we are already seeing increasing rates of disease. As the Delta variant continues to spread across the country, we expect to see increased transmissions in these communities unless we can vaccinate more people now."

Delta is the most transmissible coronavirus variant to date, and may be deadlier than its predecessors, so disease experts are particularly concerned about its spread among unvaccinated communities.

An analysis from Public Health England found that Delta was associated with a 60% increased risk of household transmission compared with the Alpha variant discovered in the UK, though more recent estimates suggest the difference is closer to 40%. The Alpha variant is already about 50% more transmissible than the original strain, according to the Centers for Disease Control and Prevention.

Researchers in Scotland also found that getting infected with the Delta variant doubled the risk of hospital admission relative to Alpha. (Previous studies have suggested that the Alpha variant may be 30 to 70% deadlier than the original strain.)

Vaccines, of course, significantly lower that risk for both variants. The Associated Press recently reported that around 99% of COVID-19 deaths in May were among unvaccinated people, based on government data.

But the US has struggled recently to convince more Americans to get vaccinated, even with incentives like cash prizes, gift cards, and tickets to sports games. Vaccination rates have fallen 85% in the last three months. As of Wednesday, the US was administering less than 430,000 daily doses, on average, compared to a peak of more than 3 million daily doses in April. The nation will likely fall shy of its goal to vaccinate 70% of adults with at least one dose by July 4 - 67% of adults have gotten at least one shot so far.

Meanwhile, Delta is expected to become the dominant strain in the US in a matter of weeks. It currently represents around 25% of the country's reported cases, Walensky said. In some regions, she added, Delta already represents nearly half of new cases.

The spread of Delta has corresponded to a roughly 10% increase in weekly average of new coronavirus cases in the US. In the last two weeks, 19 states have seen their average daily cases rise. Missouri - where roughly four dozen counties have vaccination rates below 30% - has seen cases increase 55% during that time. In Arkansas - where more than 20 counties have vaccination rates below 30% - cases have risen 63%.