(CNN) School closures that swept several US states from March to May might have led to a million fewer Covid-19 cases and saved more than 40,000 lives, a new study suggests.
The states that closed schools earlier, when the cumulative incidence of Covid-19 cases was lowest, saw the greatest declines per week at the time, compared with states that were slowest to close schools and had the highest cumulative incidence of Covid-19, according to the study, published in the medical journal JAMA on Wednesday.
The researchers -- from Cincinnati Children's Hospital Medical Center, the University of Cincinnati and the Pediatric Research in Inpatient Settings Network in Ohio -- wrote in the study that "the analyses presented here suggest that the timing of school closure plays a role in the magnitude of changes associated with school closure."
Extrapolating their findings to the US population, the researchers wrote in the study that "school closure may have been associated with approximately 1.37 million fewer cases of COVID-19 over a 26-day period and 40,600 fewer deaths over a 16-day period."
However, the researchers note their findings can not necessarily apply to current debates around reopening schools since the conditions in the spring -- when fewer people may have been wearing masks and social distancing -- differ from now.
For instance, "it is unclear how COVID-19 spread would be affected if schools remained open while states enacted other policies to restrict movement," the researchers wrote in the study. "It is possible school-related spread may be mitigated with infection-control interventions recommended by the CDC and the American Academy of Pediatrics, including frequent handwashing, universal mask policies, physical distancing measures, and increased sanitation procedures."
The new study involved examining the cumulative incidence of Covid-19 in each state per 100,000 people at the time of school closures. Those cumulative incidences for each state were separated into quartiles. The researchers used models to estimate differences in Covid-19 incidence and death between areas where schools closed and where schools remained open.
The modeling suggests that closing schools when the cumulative incidence of Covid-19 was in the lowest quartile compared with the highest quartile was associated with 128.7 fewer Covid-19 cases per 100,000 people within 26 days and 1.5 fewer Covid-19 deaths per 100,000 people over 16 days.
The study had some limitations, including that at the same time schools closed, other actions also were taken to reduce the spread of Covid-19 -- such as closing nonessential businesses and increasing the use of hand sanitizers and handwashing. More research is needed to determine the role some of those other interventions may have played in the reduction in Covid-19 illnesses and deaths.
Overall, school officials should consider the findings from the new study "in the context of an evolving evidence base" on the coronavirus, wrote Julie Donohue and Dr. Elizabeth Miller, both of the University of Pittsburgh, in an editorial that accompanied the new study in the journal JAMA on Wednesday.
"The decision to reopen schools for in-person educational instruction during the fall of 2020 is among the greatest challenges that the US has faced in generations. The decision will have life-long implications for millions of children and their families," Donohue and Miller wrote.
"In many parts of the country this has become a contentious issue, with children, their families, and teachers expressing strong opinions about what is best for them," Donohue and Miller wrote. "There has rarely been a more important time for open discussion and collaboration with a goal of reaching consensus on reopening schools, while protecting the health and well-being of students and educators during the COVID-19 pandemic."
The National Academies of Sciences, Engineering, and Medicine convened an expert committee to provide guidance on the reopening and safe operation of elementary and secondary schools for the 2020-2021 school year. That guidance was described in an opinion paper also published alongside the new study in JAMA on Wednesday.
"As school districts weigh these risks, the committee recommended that the school districts make every effort to prioritize reopening with an emphasis on providing in-person instruction for students in kindergarten-grade 5 as well as those students with special needs who might be best served by in-person instruction," Kenne Dibner and Heidi Schweingruber, both of the National Academies of Sciences, Engineering and Medicine, and Dr. Dimitri Christakis of the University of Washington in Seattle, wrote in the paper.
The committee also "called for partnerships between school districts and public health officials so that reopening decisions, plans for mitigating spread of the virus when buildings open, and decisions about future closures are all informed by the best available epidemiological and public health data and evidence," Dibner, Schweingruber and Christakis wrote in the paper.
"Just as the ability of public schools to meet the needs of their communities is contingent on available resources, so too is a community's ability to respond to the COVID-19 crisis contingent on health care infrastructure and access," Dibner, Schweingruber and Christakis wrote.
"These challenges have the potential to compound each other in ways that could be catastrophic for the most vulnerable communities. Within any answer to the question of reopening, decision makers will need to position equity at the center of their response by ensuring traditionally marginalized voices are engaged in the decision-making process, necessary services are accessible, and resources are equitably distributed," they wrote. "This moment is an opportunity to reopen schools in ways that enable them to better serve the students, families, and communities that rely on them."
The nation's top infectious disease expert Dr. Anthony Fauci said that even with every precaution taken, schools will be "part of the experiment" when it comes to learning about how the virus affects children and community spread, during a discussion Tuesday night with American Federation of Teachers President Randi Weingarten about the safety of returning to schools.
"In many respects, unfortunately, though this may sound a little scary and harsh, I don't mean it to be that way, is that you're going to be actually part of the experiment of the learning curve of what we need to know," Fauci, director of the National Institute of Allergy and Infectious Diseases, said during the Facebook livestream.
"We don't know the full impact," Fauci continued, making the point that schools have not reopened since the country initially closed down. "We don't have the total database of knowing what there is to expect."
Diving into what is known about how the virus affects children, Fauci said that studies have shown children 10 to 19 years old can spread infections to adults as easily as adults can spread infection to adults. He said what is not as clear is how infants through children who are 10 years old spread the virus.
"There are some statements, some data about that, but it is not nearly as solid as the data that we would like to see and for that regard," Fauci said when referring to what the science says about children ages 0 to 10. The NIH is currently conducting the HEROES study to learn more about this specific age group.
Although Fauci affirmed that there is no "uni-dimensional answer" to how schools should reopen he reiterated that the "default position should be that we should try to the best of our ability to get the children back to school."
After noting the benefits of returning to in-person instruction, Fauci pivoted to say that schools should only reopen for any type of in-person instruction if it is safe for the children, teachers, school personnel and the family of those people.