Travel health: yellow fever jab renewal In February my husband and I are flying from South Africa to the Victoria Falls in Zambia for three days, then returning to South Africa to finish our holiday. We have been told that we need a yellow fever vaccination certificate. We had these vaccinations in 2001, which puts us outside the 10-year limit. There was talk of these vaccinations lasting a lifetime but we cannot find any definitive answers. We are both over 60 years old and would obviously prefer not to have further vaccinations if possible. Do you know whether our 2001 certificates would be acceptable for re-entry to South Africa? We are also planning to visit Sao Tome in September - would the same principle apply? Dr Richard Dawood, travel health expert, replies Although medical experts now acknowledge that yellow fever vaccine provides long-term protection, the International Health Regulations have not yet changed, and the validity of the official Yellow Fever Certificate is unchanged - it currently lasts 10 years and after that it is invalid. It could be a long time before international agreement is reached on changing these rules. Until then, when travelling to a country that requires a valid certificate as a condition of entry, the position is clear: your certificate will have to be updated if you want to continue travelling. The issue of yellow fever vaccination in over-60s is an interesting one. Yellow fever vaccine contains live, weakened virus, and the risk of vaccine side effects is known to increase with age. However, the increased risk applies only to individuals who are being vaccinated for the first time, who therefore have no prior immunity to the vaccine virus. It does not apply to re-vaccination, so safety concerns should not be an issue. A more practical concern is the current scarcity of the vaccine itself. Supply problems began at the start of summer 2013 and remain dire. The vaccine is currently only supplied in 10-dose vials, and only a relatively small number of specialist centres have succeeded in maintaining uninterrupted supplies at reasonable cost. About Dr Richard Dawood Richard is the medical director of the Fleet Street Clinic in London and has travelled in more than 100 countries. The fifth edition of his book Travellers" Health: How to Stay Healthy Abroad is now out. He runs the Fleet Street Travel Clinic (020 7353 5678).