What is a yellow fever card?

The yellow fever card - formally the International Certificate of Vaccination or Prophylaxis, the yellow booklet - is the only vaccine document with real border power: some countries require proof of yellow fever vaccination for entry, either from all travelers or from anyone arriving from a country where yellow fever circulates. The CDC's yellow fever vaccine guidance explains the system: the vaccine is given once - one dose is considered lifetime protection under current international rules - at a designated yellow fever vaccination center, which stamps and signs your card, and the card becomes valid ten days after the shot. Arriving without it at a country that requires it can mean quarantine, vaccination at the border, or denied entry. Who needs it: travelers to tropical South America and sub-Saharan Africa where yellow fever circulates - and even travelers just transiting through a yellow fever country en route to one that demands proof. Mexico, the Caribbean, Europe, and most of Asia do not require it. The CDC destination pages list requirements country by country, and requirements change, so checking shortly before departure is standard. Practical notes: the vaccine itself is live and generally safe, but genuinely contraindicated for some - immune suppression, thymus disorders, egg allergy history - and a doctor can issue a medical waiver letter instead. Keep the card with your passport, photograph it, and note the ten-day validity gap: getting the shot three days before departure does not count. Pymander is a free AI doctor, 24/7 by text. Share your itinerary, and it can help you work out whether the card applies.