Vaccines are one of the most successful medical measures that save millions of human lives every year. With the implementation of routine immunisation programs, high and maintained vaccination coverages for many vaccine-preventable diseases – such as those against poliomyelitis or diphtheria – have been reached in most European countries and many others. Although vaccine acceptance is often high within the general population, even in countries with high vaccination coverage a significant number of children and adults are not sufficiently vaccinated because of missed opportunities or various concerns and misperceptions. [---] With increasing calls to introduce mandatory vaccination programs, intense debates on their effectiveness have also started in several European countries. There are concerns that mandatory vaccination may lead to opposing attitudes and even less vaccine uptake, particularly in those with existing critical attitudes towards vaccines; nonetheless, other studies have disproved that implementation of compulsory vaccination led to opposing attitudes and/or had negative effects. [---]