question: The nature of vaccines and the dichotomy of public opinion about their efficacy, and often the ethical debates about how they are produced, is not new phenomena. Antivaccination movements were present at the end of the 19th century and have existed in every decade, with every new vaccine, ever since. This chapter explores the origins and reasons for vaccination reluctance, sometimes medically justified, mostly based on fallacious scientific argument, and sometimes as a result of pure prejudice against government intervention in the individual’s freedom. In some cases, vaccine prejudice has been justified where vaccinees have suffered adverse effects (AEs) that have been said to be directly due to the vaccine itself, and rarely, thank goodness, to manufacturing errors that have clearly caused such effects. The analysis of the possible contributions to any observed AE, monitored by clinical trial procedures, due to manufacturing additives and adjuvants present within the vaccine sample itself, are described. The results of expert analysis of the likelihood of “cause and effect” for such AEs is described, and the improvements in vaccine technology today, particularly the immunity enhancing adjuvants, that minimize the possibility of a vaccine component’s contribution to postvaccination ill effects are reviewed. Finally, the issue of vaccine safety, of some of the concerns raised with COVID19 vaccines, and the history of cause and effect arguments for those vaccines are discussed.