Vaccines are NOT required for most countries of the world – yellow fever is the sole exception, and the rules on that one can be found on the CDC website under “travel vaccines.” Vaccines are recommended only. I’ve had the good fortune to have traveled to nearly 60 countries in my life; I’ve never been asked for a vaccine record and if a particular place required ANY vaccines, I would refuse to go there. Period.
Go to the CDC website under the ‘travel section” and read the recommendations on how to stay healthy by avoiding infections for which there are NO vaccines. The CDC recommendations on this topic are actually very good. If the suggestions work well for “no vaccine” illnesses, they will work for “vaccine preventable” infections too.
Don’t be brainwashed about how “unclean” it is in a foreign country. You may be surprised that many places thought to be primitive have standards as good, or better, than some areas of the US. If you have a HEALTHY intact immune system, you will resist infection. Travel vaccines are even less safe and some are decidedly ineffective (cholera, typhoid). Yellow fever vaccine is dangerous. Hep A is worthless vaccine and unless you plan to share needles or have sex with the natives who may be Hep B infected, why would you (or anyone) risk these injections?
The Church or the “Missionary Trip Organizers” should not require you (or your child) to be injected with potentially harmful, even deadly, substances so they can go to a foreign country to share your Faith. Personally, if I was required to take a vaccine to serve God in another country, I’d stay home and simply pray for those I was going there to serve. I would NOT be injected in exchange for voluntary service to the Church (of any denomination).