"The success of vaccines remains impressive despite the fact that all vaccines themselves present health risks of one kind or another.11 The health risks associated with vaccinations have been the basis of rare but sometimes vigorous opposition to vaccinations at least from the beginning of this century (in Jacobson v. Massachusetts, concerning mandatory smallpox vaccinations) and have reappeared more recently, leading, for example to the National Childhood Vaccine Injury Act of 1986, designed to compensate individuals for reactions to federally approved and, in some cases, legally mandated vaccines."