What makes a certificate valid
An International Certificate of Vaccination or Prophylaxis becomes valid ten days after the dose was given, and then lasts for the rest of your life. It carries your name, which must match your passport, the date, the batch and the stamp of the centre that gave it.
Three things invalidate one in practice: fewer than ten days have passed, the name does not match the passport, or the certificate is incomplete. A certificate in a maiden name is still valid, but carry the marriage certificate with it so the mismatch can be explained at a desk rather than argued about.
The ten-year expiry that no longer applies
Certificates issued before 2016 have a ten-year expiry printed on them. Since the International Health Regulations were amended, a yellow fever certificate is valid for life - including those older ones, whatever the printed date says.
Border officials occasionally have not caught up with this. If you are travelling with a certificate showing a lapsed expiry date, it remains valid and you are entitled to rely on it. We can reissue documentation reflecting the lifetime validity if you would rather not have the conversation at a border.
Lost certificates
Lifetime validity means years between uses, and certificates get lost. Where there is a record of the original vaccination we can issue a replacement, and our price list shows the charge.
Bring whatever you have: a photograph of the old certificate, a GP record, a letter from the clinic that gave it, a note of roughly when and where. The more of that you can produce, the more straightforward it is.
When you cannot have the vaccine
Yellow fever vaccine is a live vaccine and there are people who should not receive it: infants under nine months, some pregnant and breastfeeding women, people whose immune system is suppressed, those with a thymus disorder or who have had the thymus removed, and people with a genuine egg allergy.
Where a country requires a certificate and the vaccine is not safe for you, a medical exemption letter is the recognised document. We assess you and issue one where it is appropriate. Be clear about what it is: a letter explaining why you have not been vaccinated, which a border is not obliged to accept. We will tell you what to expect and what else to carry rather than send you off assuming it settles the matter.
Checking whether your route needs one at all
Two separate questions hide inside this. Is there yellow fever where I am going - and does anywhere on my route require a certificate from someone arriving from where I have been?
The second catches far more people. Countries with the mosquito but not the virus require proof from travellers arriving from affected countries, sometimes including airside transit. Bring the whole itinerary in order, with dates and transit stops, and we will work through it with the current requirements in front of us.