Yesterday I had an appointment with the Travel Assistance team (infectologia) at Hospital Aleman to check on the need of different vaccines for travel purposes and general advise. I also asked about the yellow fever vaccine. I was told that depending on age and the exact nature of the itinerary they would tell me wheather I need the yellow fever vaccine or not and wheather they could write a certificate for an exception. An appointment with "Asistencia al Viajero" would be ideal at least a month two before travelling. If necessary, the vaccine can be given at their vacunatorio.