Facing an accelerating spread of Covid-19, Italy and Japan have closed schools to impede the epidemic. Some communities in the United States have done so too, agreeing to significantly disrupt people’s lives on the theory that it will prevent deaths and serious illness.

But there is no clear evidence that such measures will slow this outbreak.

Most of what we know about the impact of school closings on disease transmission relates to influenza, to which children can be particularly vulnerable, sometimes dying or becoming seriously ill from it.

Children are important drivers of influenza infections because they have more interactions with people than do most adults and also give off more of the virus. Closing schools, it is assumed, reduces the number of contacts and thus the rate of transmission.

During the 2009 H1N1 influenza pandemic, schools across the country were closed. A C.D.C. study showed that parents largely supported these measures, but other studies found that children frequently got together outside the home or visited public sites, despite official recommendations not to do so. Fortunately, schools reopened in less than three days in most cases because data showed the flu strain wasn’t as severe as had been feared.