"One for All and All for One"

People, who have to come to an important decicision, tend to make lists of the pros and cons in order to make it an easier call. For many of us, this is also the way to figure out whether we ourselves, or our children, should get a flu shot or be vaccinated against measles. On the pro side, there is the protection against infection that we ourselves receive by getting vaccinated. On the negative side, there are the possible side-effects, or the time spent waiting at the doctor's office, for instance. But there is another important point to consider, as the research team around professor Robert Böhm of RWTH Aachen and Dr. Cornelia Betsch of Erfurt University have now proven in their study: The individual decision to get vaccinated has a benefit to society as well. This is the case, because every vaccination keeps an illness from being able to spread among the populace. Many people don't realize that if there are enough people in a society, who decide to get vaccinated, also those who are not – or cannot be – vaccinated, such as infants or the chronically ill, are protected. In this case, we can speak of community immunity or "herd immunity." When many people act on the maxim of "One for all and all for one!", diseases can even be eradicated.

In their cross-cultural study, the researchers from Aachen and Erfurt examined how the knowledge about community immunity influences vaccination decisions. In an online experiment, people from the Netherlands, the USA, Germany, Vietnam and Hong Kong were interviewed. Respondents were given either a text or an interactive simulation explaining the principle of community immunity. Others did not receive any such information. Afterwards, the participants were asked to decide on whether to get a certain fictional vaccination, or not.

The results of the study were conclusive: The willingness to get vaccinated was higher, when the principle of community immunity had been explained. "Being enlighted about community immunity leads to us think more about others when making a decision," explains Cornelia Betsch. This effect was obvious particularly in western countries – thus in Germany as well. In Asia, the willingness to get immunized was higher in general, because decisions are typically made bearing in mind the value to the common good. "It is definitely an important part of good vaccine advocacy to talk about community immunity," concludes Robert Böhm. "It makes it very clear that to get vaccinated or not is not just a decision that affects my child or me personally, but it has ramifications for all of society."

Together with Dirk Brockmann from Robert Koch Institute, the researchers have now also developed an interactive simulation, which allows everyone to experience the principle of community immunity for themselves.