It is biologically impossible to test our children to safety. A new study showed that persons infected with the Delta variant had produced around 1,000 times more copies of the virus by the time they tested positive, as compared to persons infected with the original (novel coronavirus-2019) strain. The study traced 167 infections to a single index case. A separate study traced a total of 47 cases (including 21 secondary cases) to a single person. Simply put: the Delta variant makes each of its hosts into a walking super-spreader event before the person even realizes they’ve been infected.

The practical implication of these findings is that school reopening plans that hinge on universal mask mandates and frequent testing are doomed to fail. The UK’s experience offers a real-world lesson that we, in the US, must take to heart. Despite aggressive mitigation efforts and a $4.2bn whole-of-government testing program, one in 250 schools in England have experienced at least one Delta variant outbreak in the last four weeks. The reason for the failure is obvious: children in the UK have yet to become eligible to receive the Covid-19 vaccine.

We know what we have to do. Financial services, media, and technology companies are postponing their return-to-office plans. Several states are mandating indoor masking. New York City will require proof of vaccination for indoor dining, and other major cities are poised to follow suit. Employers are stepping up their efforts to vaccinate employees; and some are even mandating Covid-19 vaccinations. We know better than to send unvaccinated and/or unmasked persons into enclosed spaces. We should extend that logic to children and the spaces they inhabit as well.