The delta covid wave carves a dividing line across the country defined by one rule: Regions with more vaccinations have fewer hospitalizations.

The map above shows places in green where most of the people are fully vaccinated and very few hospital beds are occupied by covid patients.

In purple, the map shows communities where fewer people are vaccinated and hospitals have as many as 10 times the covid patients as those in the high-vaccination areas.

Each shaded area on the map covers all the patients and all the beds in that region, which includes small hospitals and the nearby major medical centers where the sickest patients are treated.

The green regions in and around Boston; New Haven, Conn.; the Bronx in New York City; Philadelphia; Chicago; El Paso; Dubuque, Iowa; and Newark have only 3 percent to 6 percent of their hospital beds holding covid patients.

Dark purple marks the alternative places like South Carolina’s Florence, Greenville and Spartanburg, where 25 percent to 38 percent of hospital patients have covid.

In general, the rates of vaccination in each region are the inverse of hospitalization rates. In less hospitalized green zones, 50 percent of the population or more are fully vaccinated. Meanwhile, the least vaccinated purple area sits at only 21 percent. In the counties in South Carolina where hospitals have been hit hard, vaccination rates are between 35 and 42 percent.

More than a third of the country is in the high-hospitalization/low vaccination category and shaded bright purple. Another third of the country is low-hospitalization/high-vaccination green. The remainder hovers in the middle, with medium levels of covid hospitalization and vaccination rates a bit above or below the national average.

The chart above plots every hospital region on the scale combining vaccination and hospitalization. Each dot falls in the color zone that is used to portray that region in the map above.

The dots higher on the left in the shades of green have higher vaccination rates and lower numbers of covid patients in hospitals. The bottom right shades of purple have the places with less vaccination and more covid patients. There are no regions in the upper right corner with very high vaccination and also very high hospitalization. And, similarly, only two regions — in Kansas and part of Louisiana — fall in the lower left corner with low vaccination and also few patients.

Where hospitals are stressed

Even many of the high-vaccination regions are classified as covid hot spots by the Centers for Disease Control and Prevention because of steady community transmission of the highly contagious delta variant. But despite the prevalence of the virus, hospitalization remains low in those well-vaccinated communities.

Unvaccinated people are 10 times more likely to be hospitalized than fully vaccinated people, according to the latest CDC studies reviewing patients during the delta wave, which has triggered another surge in deaths.

Where a majority of the population is vaccinated

Higher vaccination rates in the Northeast, the Upper Midwest and the California coast result in swaths of green with low shares of covid patients in hospitals. Rates of cases, hospitalizations and deaths have risen since the start of summer but remain much lower than those of areas where vaccination is less prevalent.

High vaccination has worked. None of the hospital regions with vaccination above 60 percent has the extreme level of hospitalization with at least 16 percent of beds holding covid patients.

About this story

Hospitalization rates are calculated from the latest Health and Human Services weekly data on covid utilization at every hospital registered with the Centers for Medicare and Medicaid Services. Counts for beds and patients were aggregated from 5,007 individual hospitals up to Hospital Referral Regions as defined by the Dartmouth Atlas of Health Care. Beds were included for hospitals that reported no covid patients.

The share of the population that is fully vaccinated is from the Centers for Disease Control and Prevention’s county-level data except for county data from Georgia, Texas and Virginia. Data as of September 21. The share of vaccination was aggregated from counties to health-care referral regions using the MABLE Geocorr engine at the Missouri Census Data Center.