A map of each state's most and least vaccinated counties shows stark divides in the US vaccine rollout

• Across US counties, vaccination rates range from 0.1% to nearly 100%.
• The contrasts between each state's most and least vaccinated county reveal stark disparities.
• Unvaccinated communities remain vulnerable to coronavirus outbreaks.

Wherever you step foot in Martin County, North Carolina, chances are you'll encounter more fully vaccinated people than unvaccinated people. The county has the state's highest vaccination rate: more than 67%, according to the Centers for Disease Control and Prevention.

But about 210 miles west, Stanly County, North Carolina, is far more vulnerable to coronavirus outbreaks. Less than 15% of that county's population is fully vaccinated - the state's lowest vaccination rate.

North Carolina is far from the only state with such stark disparities in its vaccine rollout. Across the US, county vaccination rates range from 0.1% to nearly 100%.

The interactive map below shows the most and least vaccinated counties in each state. Hover over a county to see its vaccination rate.

In some cases, these divides form along rural and urban lines. In Kentucky, for instance, more than half the people in Franklin County are fully vaccinated. But in the more rural community of Spencer County, just 16% of the population has been fully vaccinated. The two counties are less than an hour apart.

Residents of rural counties often face more barriers to accessing shots, including a lack of transportation or internet access.

Still, plenty of rural communities have immunized large shares of their populations. In Hamilton County, New York - which has no hospital or pharmacy - the community transformed schools and a firehouse into vaccination sites. Neighborhood volunteers also teamed up to help people register for shots. Now nearly 70% of people there have been fully vaccinated, making it New York's most vaccinated county.

Individual counties are still vulnerable to outbreaks

About 41% of the US population is fully vaccinated - a much higher share than most of the world. But the pandemic is as much local as it is global, and largely unvaccinated communities are still vulnerable to outbreaks.

"When we say the United States has nearly 50% of people fully vaccinated now, that's great, but that doesn't mean anything for a particular place," Lisa Lee, an epidemiologist at Virginia Tech, recently told Insider. (Just over 50% of US adults have been vaccinated.) "We really do need to think carefully about our own situation and our own community."

Daily coronavirus cases in Missouri, for instance, have risen 2% in the past two weeks. In Reynolds, the state's least vaccinated county, daily cases have quadrupled during that time. Just 14% of Reynolds residents are fully vaccinated so far.

Ideally, scientists would like to see every county vaccinate at least 75% of its population. That's probably the threshold at which a county has reached herd immunity - the point beyond which the virus can't easily pass from person to person.

"Some places are above 60%, so there are some pockets that are pretty protected," Lee said. "We have to understand, though, that it just takes a couple of cases, a couple of people coming into a community, to pass this along."

The US continues to struggle with vaccine hesitancy: As of April, about 13% of US adults in a Kaiser Foundation poll said they wouldn't seek out a shot even if it were available to them.

Already, the nation's vaccine rollout is slowing down: At its peak in mid-April, the US was administering about 3.3 million doses a day on average, according to CDC data. Now it's administering less than 1.2 million doses a day on average.

So many states have started to offer incentives to get more shots into arms. Ohio awarded $1 million last week to a 22-year-old woman who entered the state's "vaccine lottery." California launched a $116.5 million lottery to incentivize residents to get vaccinated, while New York is piloting a program to give scratch-off lottery tickets to people at select vaccination sites.

"The hope is that if we can get enough people vaccinated, we'll get transmission to be so low that we won't have to worry about variants - that we won't give the virus a chance to figure out how to evade the vaccine," Lee said. "That's really what we're after."

This story has been updated with new data. It was originally published on May 27, 2021.

Correction: A previous version of this article stated that Franklin County is Kentucky's most populous county. That title belongs to Jefferson County.