Several northern, mostly rural states that are battling coronavirus surges with few mask mandates and low vaccine rates are now leading the nation on another preventive front: booster shots.

The rate at which fully vaccinated residents are getting the shots is highest in the states that also have high rates of new coronavirus cases, including Alaska, North Dakota and Montana, according to a review of state data by The Washington Post. In swaths of the country where health officials will not impose mask and vaccine mandates to curb the virus's spread, or have had their powers stripped away by Republican state lawmakers or governors, boosters are one of the few shields left for those worried about contracting and spreading the virus.

"It's really become impossible for local public health authorities to implement any sort of social distancing measures that could help slow down the spread," said Matt Kelley, CEO of the Montana Public Health Institute. "Getting that booster shot is one of the few tangible things that you can do to protect yourself."

Just over half of Montana's population has been fully vaccinated, ranking 35th in the nation, but nearly 1 in 5 of vaccinated Montanans received boosters, ranking second in the nation.

Montana is among a dozen states leading the nation in both infections and booster rates: Vermont, Idaho, Iowa, Wisconsin, Minnesota, Wyoming, Michigan, Colorado, Alaska, New Mexico and North Dakota. Most of those states also have had overall low vaccination rates. Vermont is an outlier with the nation's highest vaccination rate and booster rate.

Several states that successfully vaccinated the vast majority of their population - including New York, California, New Jersey and the District - have since seen a lull in new cases and a smaller share of immunized residents getting a booster. Booster rates are also low in poorly vaccinated states where infections have calmed, such as Georgia, Texas, Mississippi and North Carolina. That has worried some public health authorities.

"I think it's an unfortunate human response to not take action until it's closer to you, but the idea behind vaccines and public health is to take action now before the holidays and before winter comes," said California State Epidemiologist Erica Pan, who is urging residents of her state - where more than 6 in 10 residents are vaccinated - to not wait for their state's case numbers to rise to get their booster. She noted first and second dose vaccines picked up during the summer surge, and she suspects the state may follow a similar pattern with boosters as hospitalizations creep up, particularly in the Inland Empire.

Some low-infection states with high booster rates such as Tennessee and Kentucky are just emerging from late-summer surges of the highly contagious delta variant.

Katrina Banaski, 46, abandoned hope that her rural community of Manchester, Tenn., would take the virus more seriously. In October 2020, the town's mayor died of COVID-19, yet few of her neighbors wore masks. After being vaccinated earlier this year, Banaski said life started to return to normal - but then the delta variant arrived, local hospitals became overcrowded and her Facebook feed filled with tributes to unvaccinated people who succumbed to the virus.

"I have been fed up. I am so frustrated. I am in therapy about it, and my therapist is like, 'You can't control what other people are doing,'" said Banaski, who helps run a local coronavirus information page on Facebook. "I got the booster because I have to protect myself somehow."

In Kentucky's rural Meade County, deer farmer Michael Opie knows three people who died of COVID-19, including one during the summer surge. But the 63-year-old Marine veteran said he would have gotten a booster even without that surge because he believes following public health guidance is a no-brainer.

"If the CDC said to get another shot after six months, hey, I'm going to get it," said Opie, recalling how his father took him to get a childhood polio shot before that disease was mostly eradicated. "You got to get a flu shot every year. What's the matter with getting a coronavirus vaccine every year?"

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Coronavirus booster shots have been widely available for about three weeks, after regulators expanded eligibility on Oct. 22 and nearly 100 million Americans became qualified.

Senior citizens and adults at higher risk of severe illness because of their medical history or work are eligible for Pfizer and Moderna boosters. All adult recipients of Johnson & Johnson's vaccine, which data suggests offers less robust protection, are eligible for boosters two months after their first dose. Pfizer and its German partner BioNTech asked the Food and Drug Administration on Tuesday to authorize boosters for all adults.

Biden administration officials have hailed a recent uptick in daily vaccinations, which is fueled almost entirely by boosters and newly eligible children.

About 5.5 million people received boosters last week, accounting for 59% of shots into arms and double the number of those receiving their first doses. A majority of boosters went to people aged 65 and older. Virtually all of the first doses went to children, according to data from the Centers for Disease Control and Prevention.

Federal health officials said Wednesday at least 25 million Americans have received boosters. They continue to prioritize first doses for unvaccinated adults and newly eligible children between the ages of 5 to 11, rather than boosters for the general population.

But some states such as Alaska have placed a heavier emphasis on booster shots to stave off a winter surge.

Only 53% of Alaska residents are fully vaccinated, and the state is still in the throes of a virus wave that send cases and deaths soaring to all-time highs and forced hospitals to ration care. Health officials have distributed boosters to seniors living in small assisted-living homes scattered throughout the state and to workers in the fishing, mining and oil industries.

In the early days of the pandemic, the virus created a particularly heavy burden on miners and oil rig workers stationed in rural parts of the state, as well as fishermen who would ship out to sea for weeks at a time. Coronavirus outbreaks could sideline dozens of workers at once, forcing employees into isolation while they awaited negative tests and rode out two-week quarantines. But fully vaccinated workers only need to quarantine after exposure if they develop symptoms or test positive.

With winter approaching and a new slate of seasonal fishermen preparing to sail in about a month, state officials have been emphasizing the added security of getting a booster shot, said Lisa Rabinowitz, an emergency physician and staff physician on Alaska's COVID-19 vaccine task force.

"With waning immunity, our weather is going to force people to be inside a lot more, and there's a lot of multigenerational households," Rabinowitz said. "It was also really important that we started on booster planning early so we could increase our rates, just for protection."

Sine Anahita, a 67-year-old former sociology professor who lives in a log cabin near Fairbanks, Alaska, combs local Facebook pages to report misinformation about the vaccines, which she believes is fueling the stubbornly low vaccination rates. She feels a sense of community fraying.

"We look after each other because it's such an extreme climate we have to be bonded as a community or none of us would survive. That's something we really treasured about Alaska that has just gone away with the pandemic," said Anahita, who got her Moderna booster dose on Nov. 1. "So many people have lost that community spirit and are thinking solely in terms of themselves."

North Dakota health officials also launched a booster outreach campaign, hosting vaccine clinics at every long-term care facility in the state and mailing every vaccinated person over the age of 65 instructions for getting a booster shot.

Although only 48% of North Dakota residents are fully vaccinated, more than 37% of vaccinated people over 65 got a booster within weeks of the FDA authorizing the shot, said Molly Howell, immunization program director for the North Dakota Department of Health.

Brad Phillips, the director of long-term care operations for Thrifty White Pharmacy - one of the providers that distributed Pfizer booster shots to North Dakota's seniors - said that residents embraced booster clinics and the added protection that would allow them to continue to socialize and host family visits.

"We went to places where they were having celebrations and parties on the days we'd come on-site to vaccinate because of what it meant to them," Phillips said.

In Vermont, officials believe a surge in cases this fall plus an already widespread embrace of vaccines helped it become No. 1 in both vaccinations and boosters. Nearly 72% of residents are fully immunized and a fifth of the vaccinated received boosters.

"We've been riding this delta wave for a while and have not yet really seen much relief from it," said Kelly Dougherty, deputy commissioner at the Vermont Department of Health. "We also really promoted the heck out of boosters."

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Public health authorities in some areas that successfully immunized the majority of their population for their first and second doses are now raising alarms about their constituents not showing up for booster shots.

New Jersey prided itself on being the nation's seventh most vaccinated state, but now only 13% of vaccinated adults have received an additional dose, one of the lowest percentages in the nation. State officials said the percentage of those eligible to receive a booster is higher at 21%. To drive up those numbers, a New Jersey state vaccine call center sent 3 million text messages to vaccinated residents with information about booster shots and fielded nearly 47,000 calls to a dedicated hotline.

San Francisco officials have been urging senior citizens to get booster shots before the holidays after only one-fifth of residents over the age of 65 received an additional dose as of Oct. 25. They cited September data showing vaccinated senior citizens were being hospitalized with the coronavirus, stressing that the rates were even higher among the unvaccinated.

The share of eligible seniors receiving a booster has since increased to one-third as of Monday. Grant Colfax, San Francisco's health director, credited the growth to efforts to reduce barriers for booster shots, including mobile vans, allowing residents to self-attest they are eligible and offering boosters for parents and grandparents accompanying children for vaccinations.

He predicted San Francisco and other highly vaccinated jurisdictions where cases are low right now will eventually catch up to the likes of Alaska and Montana in giving boosters to the vaccinated.

"In some of these cases, you might see a slightly slower uptick because you have so many people eligible for a booster," Colfax said. "Because we have such high rates of vaccination, I have confidence we will see booster rates increase. I think it's really a matter of making sure people understand the importance of it going into the holiday season."