Immunizations have been saving the lives of millions of people since they were first used by Edward Jenner in 1796, and new vaccines are being developed all the time. Hopefully, a new vaccine for coronavirus disease 2019 (COVID-19) will be developed in the near future, and perhaps even one for human immunodeficiency virus. Although the effectiveness of vaccinations has been proven over the years and adverse effects to currently available vaccinations are extremely rare, many people continue to defer immunizations for themselves and their families. According to the World Health Organization (WHO), this phenomenon, known as “vaccine hesitancy,” is a major public health problem globally. This review summarizes the unproven adverse effects of various vaccines and stresses the importance of enforcing vaccination policies to minimize vaccine hesitancy. Every effort should be made to improve existing vaccines and to produce new ones, according to carefully designed scientific preclinical and clinical trials. This is particularly important in today’s era, in light of the global transparency regarding vaccination development, and the potential for future pandemics such as COVID-19.© 2020 S. Karger AG, Basel.