For more than a hundred years, two basic assumptions have been put forth by public health officials. One is that vaccines are safe. The second is that vaccines are effective for the conditions for which they're given. The public and our legislators have, by and large, accepted these assumptions as true, and as a result it is now compulsory in many states that children have as many as 33 separate inoculations before entering school. Some of these are given as early as the first few weeks of life.
Link