The worst vaccinations as far as countries NOT vaccinating are: Afghanistan, Angola, the Democratic Republic of the Congo, Ethiopia, India, Indonesia, Iraq, Nigeria, Pakistan and South Africa. As far as countries that do - the United States is the worst because they have a very alarming rate of austic children as a result of their vaccines, or at least all evidence points that way.
In Colorado, there was something called the Colorado's worst-in-the-nation measles vaccination rate if that tells you anything. As far as counties that don't vaccinate, out of the 123 million who were, billions of children in underdeveloped countries were not. It is always a heated debate where vaccinations are concerned to vaccinate or not to vaccinate that is the ongoing, unanswered question.