- A study has found a clear correlation between stronger state interventions to control the spread of COVID-19 and fewer deaths from the disease.
- Being neighbors with a state that imposed weaker interventions, however, tended to cancel out the benefits of strong control measures.
- Travel between jurisdictions with tough regulations and those with weaker regulations may partly explain the effect.
- The scientists behind the study believe that a more uniform federal response to the pandemic would have saved more lives.
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By contrast, throughout 2020, the United States government implemented no federal interventions to control the spread of the disease.
Rather, individual states decided what control measures to take and when, such as restricting public gatherings, closing schools, and imposing stay-at-home orders.
Researchers have now investigated how effective these state-level “non-pharmaceutical interventions” (NPIs) were between March 2020 and March 2021.
They have reported their findings, which have not yet gone through the peer-review process, in a preprint on medRxiv.
The research was a collaboration between the School of Medicine at the University of Pittsburgh, PA, and the Department of Statistics and Data Science at Carnegie Mellon University in Pittsburgh, PA.
More than 620,000 people have died with COVID-19 in the U.S.
“In the face of this unfathomable loss, there exists an opportunity to understand how specific NPIs may affect transmission of COVID-19 in the United States,” the authors write.
They first developed a system to score the stringency of measures in five categories:
- stay-at-home orders
- nonessential business restrictions
- indoor gathering bans
- restaurant/bar restrictions
- mask/face covering mandates
They gleaned information about control measures and how they evolved over time from the state governments’ and governors’ websites of all 50 states and the District of Columbia.
Their analysis revealed an association between stronger statewide interventions and fewer deaths, though it took at least 2 weeks before new measures had an impact on case numbers.
“Our data clearly demonstrates a negative correlation between NPI scores and COVID-19 deaths, where states with more NPI had less COVID-19 deaths,” said senior author Seema S. Lakdawala, Ph.D., associate professor of microbiology and molecular genetics at the University of Pittsburgh School of Medicine, PA.
“Based on this, it is my opinion that a uniform federal response would have saved lives and set a standard of minimum NPI amongst states,” she told Medical News Today.
Surprisingly, neighboring states tended to have similar trajectories in their case numbers over this 12-month period, even if the strength of their interventions differed.
“We discovered that some groups of states located geographically close to one another — such as in the Midwest — had similar patterns in case counts, despite the fact that their mitigation strategies were different,” says Rebecca Nugent, Ph.D., professor of statistics at Carnegie Mellon and co-author of the study.
The researchers believe that similarities in climate or demographics between neighboring states, or travel across state borders, may explain this.
“Our study did not examine interstate travel. However, we did observe that neighboring states had similar COVID-19 case curves even when the NPI restrictions were different,” said Prof. Lakdawala.
“This could have been due to interstate travel or similar climates,” she added.
She said this suggests that neighboring states should coordinate their control measures to minimize case numbers in future outbreaks.
This increased travel from jurisdictions with a high incidence of COVID-19 may lead to a rise in case numbers over the border in jurisdictions with fewer control measures in place.
“In the most severe cases, individuals not complying with policies by traveling to neighboring jurisdictions can create epidemics when the outbreak would otherwise have been contained,” write the authors of the 2020 study.