BISMARCK — In North Dakota counties with basement-level COVID-19 vaccination rates, a lack of community buy-in to the shot has translated to more infections among residents who have taken the jab, a Forum News Service analysis found.

For some with preexisting medical conditions, "breakthrough" cases of the illness can land them in the hospital despite having followed the advice of health officials to seek the vaccine.

North Dakota has recorded more than 7,000 breakthrough cases since shots became available in mid-December, though unvaccinated residents have been about five times more likely to test positive for COVID-19 than their vaccinated counterparts, according to the state Department of Health.

About 4.6% of the infections in vaccinated North Dakotans have resulted in hospitalization, and 57 residents, fewer than 1%, had died of the disease after suffering a breakthrough case as of Thursday, Oct. 14.

Breakthrough cases occur because "no vaccine is 100% perfect" at warding off a targeted illness, but health officials have strong evidence that the COVID-19 shot is effective in preventing infections that require hospitalization, said Jenny Galbraith, an immunization surveillance coordinator with the health department.

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But the risk of catching a breakthrough case is not equal across North Dakota. A Forum News Service analysis of data from the health department and the U.S. Centers for Disease Control and Prevention finds that inoculated residents of counties with low vaccination rates are more susceptible to coming down with the virus.

The western counties of Dunn, Grant and Billings led the state in breakthrough cases per capita as of Wednesday. All three counties ranked bottom five in the state in vaccination rate with less than a quarter of the eligible population opting for the shot in each jurisdiction.

Stark County, which encompasses Dickinson, ranked fourth in breakthrough cases per capita. Just 38.4% of residents 12 and older had been fully vaccinated as of Wednesday — well below the statewide rate of 53.9%.

Only one of the top 15 counties in breakthrough cases per capita has a vaccination rate above 50%. On the other end of the spectrum, more than half of eligible residents have gotten the shot in nine of the 15 counties with the lowest occurrence of breakthrough cases.

Galbraith said the findings line up with the basic principles of infection control.

"The more people you have vaccinated, the less likely the virus is able to spread," she said. "That’s the goal. We’re basically playing a numbers game with the virus.”

For health department epidemiologist Grace Njau, it's clear that unvaccinated residents of communities that have not widely adopted the shot are endangering their vaccinated but vulnerable neighbors.

Especially for older adults and those who have underlying health conditions, “breakthrough cases are an added level of risk that they can’t truly protect themselves from if other people are not vaccinated,” Njau said.

It’s unfortunate when “you’ve done everything on your end to protect yourself, but for as long as there are people who have not done the same, the virus will still circulate," Njau said. "It’s just very shocking to me that we’re still not operating like we live in a community."

North Dakota Department of Health epidemiologist Grace Njau. Photo provided
North Dakota Department of Health epidemiologist Grace Njau. Photo provided

The vaccine is believed to have slightly diminished effectiveness against the highly contagious and now dominant delta strain of the virus, Njau said, adding that immunocompromised people may have waning immunity anyway since they received their doses of the vaccine as many as 10 months ago. That's why it's so imperative for unvaccinated North Dakotans to get the shot, even if they're not concerned for their own health, Njau and Galbraith said.

Galbraith noted that since the vaccine is not a perfect solution for preventing illness, vaccinated residents should continue with other virus-mitigation practices like mask-wearing.

Njau forecasts that breakthrough cases will become a larger share of the state's active COVID-19 infections as more unvaccinated residents contract and recover from the illness, but she maintains that widespread vaccination is the best protection for the state on the whole.