The white paper card that most Americans rely on today as proof of vaccination against covid-19 doesn’t fit unfolded inside your average wallet — and that’s only one of many reasons digital credentials are needed now more than ever.

The highly transmissible delta variant of the coronavirus has ushered in mask mandates in some places, but vaccination remains the key to containing the pandemic once and for all. Vaccinated people are far less likely than the unvaccinated to contract the virus and even less likely to become seriously ill. These facts make the case for organizations, at a minimum, to be permitted to require vaccination for in-person activity. Employers should be able to insist that workers be immunized; restaurants, the same for their customers.

Several states have blocked or attempted to block government agencies, local businesses or both from mandating vaccination, with Florida Gov. Ron DeSantis (R) leading the way — efforts that fly in the face of the values of liberty that their proponents purport to defend. Thankfully, another contingent of states has either left entities free to do as they please or encouraged them to write rules that fit the times. New York City became the first U.S. city this week to require proof of vaccination for a variety of indoor activities. Those states should be doing whatever they can to smooth the process by which constituents can show they’re immunized, and that means developing a smartphone-compatible certificate that’s easily downloadable and easily scannable.

New York already has such a system in its Excelsior Pass, and a handful of other states, including California and Louisiana, also provide portals for downloading information fully authenticated by authorities. A few nonprofits as well as for-profits, such as the airport security service Clear, have developed apps of their own that allow for CDC card scanning — but Americans will benefit most from an option that’s universally accepted as well as difficult to fake. After all, the thriving black market for those paper cards has already proved the allure of counterfeits.

Excelsior Pass-style systems should be possible in every state. The practical roadblocks, however, will vary depending on the quality of immunization registries; some are better than others at coordinating with pharmacies and other providers to put every citizen in the system. Those states that are better should aid those that are worse by offering to share source code. Common standards would generally be a boon to interstate activity, and a consortium of states interested in establishing shared protocols could do a great deal of good. So would technological support at the federal level. Privacy and accessibility should also be on policymakers’ minds. States will have to ensure that those without smartphones also have a way to participate in everyday life.

At the least, enabling vaccine requirements will help organizations keep their spaces safer. At best, they also could inspire some holdouts to get the shot at long last.