Even as the pandemic approaches its third year, there’s no such thing as a vaccination passport in the United States. So how do you prove that you’ve been vaccinated and boosted when you travel internationally?

I had to answer that question quickly when I landed recently on the Azorean island of São Miguel. Officials ushered arriving passengers into a long line and asked to see our Certificado de Vacinação, also known as the European Union’s “digital green certificate.” I didn’t have one. And there is no U.S. equivalent.

“Unfortunately, given the patchwork approach to vaccine passports in the U.S. — with some states offering some form of vaccine passport and others banning vaccine passports — it would be nearly impractical for a foreign government to recognize a U.S.-based application,” explains Bob Bacheler, managing director of Flying Angels, a non-emergency medical transport service.

And so began an adventure that many Americans have probably experienced. How do you prove you’ve been vaccinated? Can you get a foreign vaccine passport? And what if you can’t prove you’ve been vaccinated?

I hoped the solution would be my Yellow Card, also known as the International Certificate of Vaccination or Prophylaxis. I wrote about the Yellow Card in an earlier column, and when I had my vaccine doses and booster shot, I asked the nurse to fill out my Yellow Card and my Centers for Disease Control and Prevention coronavirus vaccination record card.

The Azorean official accepted my Yellow Card. She also okayed my 19-year-old son’s Yellow Card. But when she opened my 16-year-old son’s card, she said we had “um problema.”

When he finished his vaccination series this summer, he had forgotten to ask the pharmacist to fill out the Yellow Card in addition to his CDC card.

“Look,” I murmured, barely able to keep my eyes open after more than 30 hours of flying. “Can't I just fill out the information on his Yellow Card?”

“No,” she insisted. It needed to be done by a medical professional.

Finally, I offered her his expired PCR test, taken almost four days previously in Los Angeles. She waved us through. In the van on the way to our hotel, I filled out my son’s Yellow Card with his CDC vaccine information.

But can you simply get a foreign vaccine certificate? Alan Oakes did. The retired magazine publisher from Laguna Hills, Calif., has made two trips to France since the pandemic started. This past summer, French authorities announced that foreign nationals could qualify for a TousAntiCovid pass — the France digital covid pass. In November, on their most recent visit, Oakes and his wife applied for the pass and received it. But they didn’t really need it.

“We showed our handwritten U.S.A. CDC pass and had no issues,” he says.

Andy Abramson, a frequent air traveler who runs a communications firm in Los Angeles, also obtained a French vaccine passport this past fall. He found that the QR code it generated allowed him to move between European countries.

Getting a vaccine passport in France is pretty straightforward. You can go to any pharmacy and pay about $40 to verify your status. You have to bring your passport and original vaccination certificate, then download the TousAntiCovid app. That’s what Jack Ezon, founder of Embark Beyond, a travel agency, did when he visited Paris recently.

An insider tip: Most luxury hotels in France will get a vaccine certificate for you. “Just drop your passport, vaccine certificate and fill out a form, and you’ll have a QR code delivered to your room,” Ezon says.

You can obtain an E.U. digital green certificate when you’re in Europe at a pharmacy or testing center. For example, if you’re headed to Barcelona this spring, you can apply for a certificate at any test center accredited by the Catalan Health Service, CatSalut. Readers have also reported that they have applied for a E.U. digital green certificate at French pharmacies. Paperwork requirements vary. Some will accept your U.S. cards as proof of vaccination, while others may require a PCR or antigen test.

If you can’t get a vaccine passport like the E.U.’s digital green certificate, you can always try to use the vaccination record you have. That’s right: the CDC card you were given when you were vaccinated. That’s what Jeff O’Hara​ did when he visited Germany recently. He found that the certificates were required almost everywhere he went.

“I had a picture of my CDC card saved on my phone,” he says. It worked every time, says O’Hara, who runs an event management firm in New Orleans. Just to be safe, O’Hara also recommends having an app such as Airside or VerifFly in case someone questions your card.

Craig Zapatka, co-founder of the travel planning site Elsewhere, says the stakes are pretty low once you’re in your destination country.

“There have been only a few very special incidents where our travelers have been rejected, and only in Western Europe,” he says. “But the incidents did not in any way affect the overall travel experience. They occurred at a nightlife event and a few cafes.”

And if you don’t have the proof you need? In São Miguel, where my sons and I had our paperwork trouble, the agent said we could take a quick antigen test, then enter the country. But I’ve also seen officials in Europe wave travelers through, even when their documentation isn’t perfect.

Maybe that’s the most important takeaway when it comes to foreign vaccine passports: In the end, having one may not even matter.