The White House has made clear that directly imposing a national requirement on the general populace isn’t on the table, in part because many would question the government’s authority to do so in our constitutional system of limited federal powers. And, in fact, the government has never issued a national vaccination mandate—perhaps because, in the past, leaving that role to states and localities has sufficiently contained epidemics. If any federal statute currently provides authorization for a national covid-vaccination mandate, however, it would be the Public Health Service Act, which gives several agencies the authority “to prevent the introduction, transmission, or spread of communicable diseases” from foreign countries or between states. The government can use this law to pursue quarantine policies, and the statute, broadly construed, may also allow the government to mandate vaccinations to prevent interstate spread of covid-19.

Alternatively, Congress could rely on the Spending Clause to pass new laws that condition the transfer of federal funds to a state upon its establishing a vaccination mandate. Congress could also use the Commerce Clause to institute a national requirement as a regulation of interstate commerce. But those sweepingly ambitious federal routes are guaranteed to become mired in tremendous political pushback that could ultimately increase public resistance to vaccination, not to mention constitutional challenges claiming federal overreach. Short of those methods, the federal government still has myriad ways that it may yet push states, institutions, and citizens to do more than they otherwise would, with an arsenal of inducements, pressures, conditions, and threats. Depending on how things progress with the coronavirus variants, a national vaccination mandate may remain possible as a last resort.