If you have been fortunate enough to receive a COVID-19 vaccine, you also possess an essential, high-tech tool for proving your immunity to others.

Just kidding, it’s a piece of cardstock. On the flimsy rectangle that all Americans get with their shots, doctors and pharmacists record dates of administration, vaccine type, and lot number. Some scrawl the information by hand with a pen; others apply a preprinted sticker. The cards offer no special marker to prove their authenticity, no scannable code to connect to a digital record. At three by four inches, they’re even too awkwardly sized to fit in a wallet. A mid-century polio-vaccine card doesn’t look too different from today’s COVID-19 vaccination records.

Distributed by the CDC to those administering the vaccines, these cards are supposed to help recipients get the correct second dose, if needed, and offer a personal record, Jason Schwartz, a Yale public-health professor, told me. But they’ve taken on a considerably grander importance as pandemic restrictions have eased in the United States—especially now that the CDC has okayed vaccinated people going maskless in most places—because they’re the only thing available to all Americans that shows someone has been vaccinated. When you get a COVID-19 shot, the information goes into a digital record kept by the state where it was administered, and that’s the end of the road. The CDC does not hold records of individual vaccinations, and the White House has indicated that it has no plans for a federal database. (Neither the CDC nor the Department of Defense, which ran the Operation Warp Speed vaccine program, responded to my requests for comment.)

This setup has made things complicated for businesses, employers, universities, restaurants, concert halls, airlines, and any other institutions that want to verify people’s vaccination status as the country reopens. It’s easy to say that customers, employees, or students need to be vaccinated, but it’s much more difficult to check that someone really is. A few states have created or promised more technical “vaccine passport” systems—usually smartphone apps connected to state databases—that could confirm people have been vaccinated against COVID-19. But many Republican-led states, including Texas, Florida, and Arizona, have opposed or even banned the implementation of any sort of vaccine verification system, mostly citing government overreach.

The verification methods that places choose, if any, will certainly influence people’s behavior. At the same time, what requiring an immunization means is easy to misconstrue. America is simply past the point when any system could reasonably offer a foolproof, fraud-proof, universal method of confirming that someone has gotten a COVID-19 shot—flimsy cards and scattered apps included. Instead, we are bound to rely on the same method Americans have always had when it comes to proving vaccination: an honor system built on mutual trust.

In many cases, the imminent future of vaccine verification will probably follow the model of a cashier who asks for ID when you present a credit card. In the same way that the cashier looks to see that it is an ID, or that the photo matches your face, a vaccination gatekeeper might glance at a piece of paper or your phone screen to check that some sort of documentation exists—and not, for instance, scan anything to confirm that the document is legitimate and that antibodies are indeed coursing through your tissue and blood.

Especially in verification-shy states, things might not even go that far; citizens will “prove” their status by simple attestation. But for any place that decides to require a vaccine card or passport for entry, the cashier method won’t validate much either. Given the political animus and misinformation surrounding COVID-19 policies of all kinds, it’s no surprise that some opponents of vaccination realized they could abuse that trust by buying or stealing blank vaccination cards. Earlier this month, the owner of a bar in California was charged with selling fraudulent cards. In The Washington Post’s coverage of the arrest, a security expert estimated that forgery “is more widespread than we even think at this point.”

Digital vaccine-passport systems overcome vaccine cards’ awkward physicality, but just as hygiene theater turned cleaning into a false sense of pandemic security, vaccine passports risk becoming verification theater, especially if deployed in only a small number of states. In March, New York launched Excelsior Pass, a free app that claims to provide secure vaccine verification for entry into venues such as theaters and stadiums. Hawaii plans to introduce a system backed by the same company, and California has adopted a policy that seems to require a similar app. Excelsior Pass does plug into state databases to produce a screen or printout with a bar code that can be scanned by another app. But this is all limited by the fact that the databases record only shots administered in New York State. And the app isn’t magic; not much is stopping someone from sharing their own screenshots or printouts with someone else.

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When I asked an Excelsior Pass help-desk agent how a business could confirm that a pass actually belonged to its holder, she said it was the first time anyone had asked that question. “As far as I know, there is no way,” she said. A vaccine-scanning agent could check the pass against a holder’s ID, but only a name and date of birth appear on the Excelsior Pass anyway. The New York governor’s office told me that hundreds of thousands of New Yorkers are downloading Excelsior Pass each day, and that “passes must be verified against a photo ID.” In a high-traffic environment such as a stadium or even a restaurant, though, it’s hard to believe that everyone will take the time to do so.

None of this is to say that lying and forgery will necessarily be as big of a problem as some coverage has suggested. Millions and millions of Americans have received a shot or are eager to get one. And just because faking it is possible doesn’t mean that most people who oppose vaccinations will happily leap into deceit. (In March, the FBI warned that producing or purchasing vaccine cards is illegal.) But any practical consideration of COVID-19 vaccination requirements in the U.S. has to contend with the fact that hopes to require vaccinations in the first place only go so far.

Other countries may not be better off. Some have devised a variety of high- and low-tech solutions to provide universal vaccination verification, including a European Union–wide digital pass and printable QR codes in Israel, which have limitations similar to those of the U.S. systems. But America’s scattershot, state-specific approach makes meaningful, widespread verification all the more a fantasy.

Don’t we confirm vaccination status all the time, and for much less scary diseases? No, we do not. Vaccine mandates can effectivelyincrease immunization rates, but mandate has mostly meant encouragement, not requiring demonstrable evidence. Vaccine verification in America has been janky from the start. Vaccinations have always been recorded primarily on paper, and evidence of immunity has always been based largely on trust.

Real verification of any vaccination remains, at the most basic level, pretty difficult. Every state maintains an immunization registry that records new vaccinations, but no matter the state, these systems record only vaccines administered in the state. If you move, your new physician could record your earlier shots on a paper record, but not an electronic one. In this way, digital vaccination records are typically less complete than paper ones. And nearly all states allow citizens to opt out of the vaccine registry anyway.

Citizens usually can’t access their own records, and when they can, the process is not fast or easy. In some states, only medical offices can access digital vaccine records; in others, select agencies such as child-care facilities and schools are authorized to access them. Many companies are planning to mandate COVID-19 vaccines, which is perfectly legal under certain conditions, but these mandates can’t amount to much more than asking employees if they’ve gotten a shot. Even then, exemptions would likely be in place for reasons of disability or religion—and medical inquiries of certain kinds might run afoul of the Americans With Disabilities Act.

The most common reason to need an immunization record is to enroll in school. In Georgia, where I live, new students must file a document, Form 3231, before they can register. A physician is supposed to fill out this form, which amounts to little more than a series of blank fields for various immunization dates. An FAQ from the Georgia Department of Public Health indicates that “only health departments and physicians licensed in Georgia can obtain blank immunization certificates,” presumably to control access to this official record in order to prevent misuse. But when I performed a simple Google search for Form 3231, the third result linked to exactly that, a blank immunization form. If someone wanted to, they could easily falsify the dates and claim inoculations they hadn’t really gotten. (The Georgia Department of Public Health didn’t respond to my request for comment.)

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One big difference between an immunization record and a COVID-19 vaccination card is that the official record is signed by a health-care provider. Forging this signature could amount to committing a felony in all 50 states. This appears easy enough to get around: Some vaccine-record fraud has been perpetratedby complicit doctors. But also, the data on these forms might hardly be verified in the first place. Schwartz, whose research at Yale focuses on the history and public policy of vaccination, suspects that these documents are checked to see if they look like medical records, but not for much else. “If it passes that very low bar of looking plausibly accurate, I suspect that is considered good enough,” he said.

Even international verification faces similar limitations. In the case of vaccines recommended or required for travel abroad (such as those for yellow fever, typhoid, and rabies), most countries rely on the International Certificate of Vaccination or Prophylaxis, provided by the World Health Organization. That instrument is—wait for it—a yellow card with written inoculation records accompanied by medical stamps or signatures.

America’s resolutely patchwork approach to vaccine verification is not a failure of imagination. Schwartz noted that the technical hurdle is relatively surmountable; given verifiable vaccine billings to Medicare, Medicaid, and private insurers, along with the state databases, you could get a pretty comprehensive accounting. Eventually, in theory, some aggregation of state immunization registries could make the fantasy of a countrywide vaccine passport a reality.

But the U.S. has already chosen a different path. Introducing a universal vaccine passport would not change the cultural, psychological, and civil-libertarian resistance to a national medical-certification system. When vaccination becomes an amorphous, cosmic battle of national political division, getting people to accept inoculations—which is the goal—becomes even harder. The existing record-keeping system has worked well enough over the years, and so it will likely persist: Scribbles on sheets of paper, some signed and some not, will corroborate protection. COVID-19 vaccination cards will give way to … more cards or papers, probably. Perhaps signed by a doctor this time. Perhaps with a bar code that systems such as Excelsior Pass might read. The honor system will persist too, like it does with most documents and identification.

If you’re a vociferous vaccine advocate, this can easily sound disheartening. But that shouldn’t necessarily be the case. Remember that mandates have mostly meant strong, official encouragements, not verifications. On the one hand, it’s understandable to be wary of going much further: In China, COVID-19 tracking has expanded the nation’s already concerning use of health data for citizen monitoring. On the other hand, the solutions currently on offer in the U.S. overlook the fact that the main hurdles to vaccine mandates are not technological. The whole vaccination apparatus just hasn’t sought this level of verifiable confirmation before.

But verifiable confirmation is exactly what vaccine passport implies. That makes it a wrongheaded way to understand vaccine record-keeping. Vaccination records aren’t even trying to be secure, official documents, like driver’s licenses and passports. Instead, they are more like paper contracts—documents whose contents become “true” given a medical professional’s imprimatur or review. A “passport” suggests a universal infrastructure for recording, documenting, retrieving, and analyzing changing vaccination information in real time. That is not our actual situation.

For Schwartz, the core challenge for vaccines as a part of public health doesn’t have much to do with verifying inoculations. Rather, it has to do with striking an appropriate balance between carrots and sticks. Without widespread support for vaccination, and the COVID-19 vaccines in particular, the ability to enforce its uptake will fail. “I worry about passports and permission to travel becoming the focal point,” Schwartz said, “when we really need to focus on helping to sell these vaccines.”

To do that, it might be better to reframe what a “vaccine mandate” really means. Instead of an impersonal, technical ratification infrastructure, it boils down to asking people if they would please get vaccinated, and trusting that they have if they say they have. To accomplish that goal, Schwartz has a decidedly low-tech suggestion: “Focus on the preexisting communities where we have relationships and bonds.” Workplaces and schools, where people are already bound to others in an organic way, are a good place to start. According to Schwartz, if an organization you trust, such as your office or school, leads the charge from the grass roots in encouraging its community to get shots, more people are likely to do so, even if the documentation is imperfect. Extra incentives, whether in the form of free donutscash lotteries, or mask-free living, can also help. From there, the immunity conferred by a commitment to act safely among schoolmates or work colleagues would carry over to restaurants, airplanes, and concert venues. It’s more manageable than a top-down system of compliance, to which Americans respond poorly.

No matter the appeal of a universal certification that would give businesses, airlines, theaters, and the public who uses them peace of mind about the vaccination status of those around them, Schwartz considers the cultural barriers to implementing such a system “insurmountable.” Establishing and relying on real mutual trust among citizens shouldn’t feel silly or foolish. That is not the current condition in America, to be sure. But we would be remiss to give up its possibility or dream of replacing it for good with an app.