My parents are doing a 4 month cruise through 26 countries and it is highly suggested that they get the MMR and they can’t go ashore in one country if they don’t have the Polio vaccine. I have a 6 week old (not vaccinating at all) who will be 4 months at the time they leave. They are looking into the vaccines to see if they really want them, but I was hoping that someone might know how long the vaccines shed for since they are live vaccines and what the chance would be for my son to get anything from them. Thanks in advance!