By M. Kate Grabowski and Justin Lessler / Special To The Washington Post

Schools nationwide are returning from winter break this week; either virtually or in person. The Centers for Disease Control and Prevention recently put out recommendations that schools, especially kindergarten through fifth grade, should be the last thing to close and the first to open during the pandemic response.

We wholeheartedly agree with this recommendation. But that’s not because schools do not contribute to viral transmission, as many commentators have argued. Based on evidence currently available, schools almost certainly do contribute to viral transmission, and pretending they don’t is potentially dangerous, as it could lead to schools opening without proper preparation and investment in virus control.

We should open schools not because it would be risk-free, but because schools are important, and the risks can be managed.

Closing schools does help slow transmission of the virus. Multiple studies in the United States, Europe and elsewhere have shown that school closure has been associated with substantial reductions in community spread of covid-19. In many places, school closure had the strongest associations with reduced transmission of all control policies.

It is likely that these strong associations have a lot to do with things other than transmission in schools themselves. Early in the pandemic, school closure was one of the strongest markers of when communities started taking the threat of the virus seriously, and closing schools was usually one of the first interventions implemented. Once closed in the spring, schools remained closed for in-person learning in most places in the United States throughout the summer, thanks to the usual vacation schedule. But because school closure is a marker of how seriously communities were taking the virus, they first closed right around the time that people started making a lot of other non-mandated behavior changes that helped to contain virus spread. Closing schools itself also leads to behavior change, of course, as the need for people to stay home with children changes their patterns of social interaction in ways that can limit transmission.

But even if these factors explain some of the association between school closure and reduced transmission, the association is so strong that it strains credulity to claim that schools play no role in driving viral spread. Not only is there a strong association between school closure and reduced transmission in almost every study, there have also been numerous outbreaks associated with schools, day cares and camps. Schools are already known to drive transmission of other respiratory viruses, such as the flu and measles, both because of the frequency and closeness of interactions in school buildings and the ways in which schools bridge communities that might not otherwise interact. For schools not to be a major driver of covid-19 transmission, something would have to be very different about this virus.

The thing people often point to as being different about covid-19 is that children seem to be less likely to be infected with and transmit the virus than adults. Most studies support this conjecture, and young children appear to be about one-half to one-third as likely to be infected by an infectious household member as working-age adults are. The evidence about transmission is less clear, though children are less likely to have symptoms and asymptomatic individuals are less likely to transmit. But even so, while they’re in school, children have many more interactions than typical in adults. Without effective mitigation measures, that could wash out their reduced susceptibility; potentially explaining similar or higher attack rates in young children in some school and camp outbreaks.

Many have seized on these moderate reductions in susceptibility and the relatively low number of reported “super spreading” events in schools to argue that schools are not major drivers of community transmission. But schools can still be the home of outbreaks and drive community transmission. Even if attack rates in schools and the community appear to be similar, schools play an unique role in U.S. social life, and they link households and communities that may otherwise be unlikely to interact, providing opportunity for the virus to jump between them.

And yet despite these risks, we strongly believe every effort should be made to keep schools open for in-person classes. Not only have studies repeatedly shown the importance of early-childhood education for success in life, but in many communities, schools are the primary way in which food and other essential services are provided to poor students; the same students who are often worst-positioned to take advantage of online education. School closures have also placed a disproportionate burden on lower-income families and communities.

The trick is to open schools safely. Mitigation measures such as required masking, class cohorting and physical barriers between desks can go a long way in reducing covid-19 transmission. Different strategies should be developed for elementary-age children than for older students, because there are differences in the importance of schooling by age and because older children appear to be more susceptible to the virus compared with younger ones. Critically, teachers need to feel safe and supported; without their buy-in, in-person learning is impossible. In particular, teachers should be near the front of the line when it comes to vaccination.

Doing all that requires planning and resources; investments that have been inconsistently made across school districts. And it also requires frank and open conversations among stakeholders, which might be even more difficult than finding time and money for mitigation efforts.

The barriers to doing so became evident to us even as we worked on this essay. A teacher who saw an early draft thought some of what we said would be used to justify opening schools without proper safety measures in place, while a parent who saw the same version felt that it would be used to justify closing schools until the virus is completely gone.

We can only move forward safely with in-person learning by being honest about the risks posed by covid-19 in schools and the ways in which we can overcome them. If we fail to find a balanced path forward, we will be forced to either put teachers, students and families at risk from the virus or force them to suffer the costs of closed schools for many more months while we wait for the vaccine to curb transmission.

M. Kate Grabowski is an assistant professor of pathology and epidemiology at Johns Hopkins University and co-director of the Johns Hopkins Novel Coronavirus Research Compendium. Justin Lessler is an associate professor of epidemiology at the Johns Hopkins University Bloomberg School of Public Health.