Thanks to vaccines, many people are not exposed to the risks associated with vaccine-preventable diseases (VPDs). This, however, results in growing popularity of antivaccine movements and affects global and local epidemiological situation. Vaccine hesitancy has become a significant problem not only for epidemiologists but also for practitioners. Fortunately, the hesitant group seems to be vulnerable to intervention, and studies indicate that these patients can be persuaded to undergo vaccinations. The aim of the present study was to determine the factors most strongly affecting vaccination-related attitudes and decisions. An anonymous, self-administered survey consisting of demographic data and single select multiple-choice questions regarding vaccination was conducted. The voluntary study included secondary school pupils, medical and nonmedical students, healthcare professionals, hospital and clinic patients as well as parents. A total of 7950 survey forms were distributed between January 2018 and June 2019 in south-eastern Poland. A total of 6432 respondents (80.2%) completed a questionnaire that was eligible for analysis. The positive attitude toward vaccination was significantly affected by older age, by the fact of obtaining information on vaccinations from a physician, this information’s higher quality (assessed in school grade scale), higher level of knowledge on vaccines and by the fact of denying the association between vaccination and autism in children (p < 0.001). The probability of supporting vaccinations was almost eight-fold lower among respondents believing the vaccine–autism relationship. Chance of supporting vaccination doubled in the group with a higher knowledge level. The individuals not provided with expert information on vaccination were twice as often unconvinced. Age, education and having children significantly affected the attitude toward influenza immunization (p < 0.001). Older, better educated respondents and those having children were more positive about vaccinations. The medical community still exert decisive effects on attitudes toward vaccinations. High-quality information provided by them is of great importance. Skillful and competent provision of evidence-based information disproving the myth about vaccine–autism connection and proper education of medical staff is essential in molding positive attitudes toward vaccinations.