The United States has the dubious honor of suffering the highest COVID-19 death rate of any high-income country in the world. But that national average — 372 deaths per 100,000 people as of last summer — obscures the fact that pandemic outcomes have varied greatly from state to state.

In a comparison that took into account demographic differences between states, Arizona’s COVID-19 death rate of 581 deaths per 100,000 residents was almost four times higher than Hawaii’s, which had 147 deaths per 100,000 residents. The death rate in the hardest-hit US states resembled the death rate in countries with no health infrastructure at all. The top-performing states were on par with countries like Australia, New Zealand and South Korea, which have been working hard to keep the death toll from the pandemic low.

What explains these huge differences? New research offers some intriguing answers.

The researchers found that race, ethnicity, and socioeconomic factors were the strongest predictors of the state’s COVID-19 death toll. The higher the proportion of residents who identified themselves as black or Hispanic, the higher the poverty rate, the higher the proportion of residents without health insurance, and the lower the level of adult education, the more deaths per capita.

This may not be a big surprise. But the researchers also found that the more people in a state trust each other, the lower their collective risk of dying from COVID-19. This result highlights how growing divisions in America have made us especially vulnerable during the pandemic.

“How do we feel about another issue,” said the political scientist Thomas J. Bollyk, one of the lead authors of the study. “Solidarity between people—the feeling that others will do the right thing, and you don’t take advantage of it—is an important factor in your willingness to adopt defensive behavior.”

The report, published last week in the Lancet medical journal, is based on a dataset of the US pandemic from January 2020 to July 2022. Bollike called the event “the most comprehensive statement to date on the factors influencing pandemic outcomes.”

Dozens of researchers across the country have pulled data on state demographics before the pandemic, looking for ways in which their behavior and policies have diverged as the pandemic has evolved. To make direct comparisons across states, they created standardized infection and death rates that accounted for differences in factors associated with COVID, such as age and underlying health conditions of residents.

For example, California’s unadjusted COVID-19 death rate of 291 cases per 100,000 residents was lower than all but 11 states. But once studies took into account that the state has a relatively young population with a low prevalence of conditions that make people vulnerable to severe cases of COVID-19, the death rate has risen to 418 deaths per 100,000 inhabitants. The authors of the study found that only 15 states fared worse.

Demographics told only part of the story. Political decisions also mattered.

Most states adopted some sort of mask-wearing and social distancing requirements early in the pandemic, but there were wide variations in how strict they were and how long they lasted. When the researchers assigned each state a “mandate propensity,” they found that states that scored high for implementing public health measures had lower rates of coronavirus infection.

California had the highest propensity for mandates, while Oklahoma had the lowest. The researchers calculated that if Oklahoma implemented masking and social distancing restrictions to the same extent as California, Oklahoma would have 32% fewer cases of coronavirus infection.

However, more aggressive public health measures have not resulted in a reduction in the death rate. The authors suggest that this is likely due to the fact that many elderly and sick people who are most likely to die if infected have taken steps to protect themselves, whether or not their state governments issued strict regulations.

The researchers also found that a state’s propensity to mandate had no effect on the health of its economy, as measured by its major domestic product. States with less mask use and fewer restaurants closed did have higher employment rates, but this additional economic activity came at a cost: every percentage point of increase in state employment was associated with 143 additional deaths per 100,000 residents.

No single factor was more important than “vaccinated man-days” – a measure of how the population of the state was vaccinatedand how early. The researchers estimate that if Alabama, which scores the lowest on this measure, achieved the vaccination coverage seen in Vermont, the highest-ranked state, there would have been 30% fewer infections and 35% fewer COVID deaths during the study period. -19. .

Another noteworthy finding, the authors write, is that vaccination requirements for civil servants, which have caused a lot of legal trouble, have been “distinguished” by their association with lower infection rates and fewer deaths.

Map comparing cumulative coronavirus infection rates by state, standardized to account for population differences.

(Bolliki et al., The Lancet)

The study highlights the tangible loss of the country’s “us versus them” mentality, which came to full fruition during the debate about mask-wearing in schools and vaccination requirements for government employees. We don’t really trust each other, which makes us less likely to do things to protect each other.

“Interpersonal trust” has been measured since the 1950s, and since the early 1990s, levels of this positive feeling towards others have dropped dramatically in the United States, said Bollike, head of the research center. Global Health Program at the Council on Foreign Relations. This trend was driven by deteriorating economic conditions for low-income people with higher education. It is especially low among black Americans and among those who voted for Donald Trump in the 2020 election.

Trust in the federal government and trust in science have not been reported as major contributors to COVID-19 deaths. But trust in fellow citizens is strongly ingrained, Bollike said.

The links found during the study clearly indicate that the strengths and weaknesses that states use in a national emergency, as well as some of the policies they adopt to respond to a crisis, matter a lot, he said. Lawrence Gostinexpert in public health law at Georgetown University.

“This is strong evidence that governments have taken COVID seriously, used science and mitigated health inequalities,” Gostin said. “Much of the political rhetoric — that mandates don’t work and that justice isn’t important — has turned out to be wrong.”

According to him, the results of the study can be used to save lives long before the next pandemic. Dr. Stephen Wolfresearcher at Virginia Commonwealth University who tracks the health of Americans.

“Many of the same factors are affecting health right now,” Wolfe said.