Vaccines for travelers
What shots you need to get for travel to Asia, South America, Africa, and Europe
The developing world
For trips to the developing world or more exotic locales, it's best to get any recommended vaccines.
These are usually against things like Hepatitis A and B, Japanese encephalitis, typhoid, and cholera.
The recommneded vaccines vary from place to place—and for the types of areas in which you will be traveling. If you will only stick to urban areas, often the list will be shorter than if you explain to your doctor that you plan to visit rural or wilderness areas, for which a greater number of vaccines are often recommended.
My philosophy: Get vaccinated against anything you might potentially encounter in a region, regardless of your current travel plans. You never know. You may have intended only to visit the capital city, but once there decide to take a day or two to make a trek into the jungle or hinterlands. Best to abide by the Boy Scout motto: "Be Prepared."
Yellow fever and Africa and South America
The only typically required vaccine is against yellow fever for travel to sub-Saharan Africa and tropical South America.
(What I mean by "required" is that, while you can usually get into those countries just fine, other countries might not subsequntly let you in if they see by your passport that you have been to those yellow fever hot zones unless you can produce proof that you were first vaccinated.)
More information on travel vaccines
Get full lists on required and recommended vaccines for travel at: