I have taken a number of vaccinations and I do have an auto immune problem. In my case I would rather risk a vaccine, than trying to tackle something like yellow fever. These unusual diseases, we really don't have any immuninty to. If you have a weakened immune system the disease would be difficult on you. I am just a believer in the shots. Your PCP can tell you of the risk of that particular injection, or a disease specialist would know about that disease and its risks as well. Hope you have a great time going to a new continent. Good journey. ginnie