Most choices that people make about their health, such as choosing to exercise regularly or opting for a healthier diet, primarily affect their own health and well-being. However, some health decisions can have far-reaching consequences that extend beyond the individual. For instance, most vaccines not only protect the person who is vaccinated but also help to protect other people around them.

Herd immunity occurs when a high enough proportion (depending on the contagiousness of the disease) of a population is vaccinated to reduce the spread of an infectious disease in the community. Herd immunity offers indirect protection for vulnerable populations, such as children, older individuals and those with compromised immune systems who cannot be vaccinated for medical reasons or for whom vaccines are less effective. Because some health decisions have both individual and collective benefits, understanding the social implications of health decisions can have an important role in the decision-making process.

In a 2017 paper, Betsch and colleagues assessed whether communicating the concept of herd immunity encourages vaccination uptake, using data from more than 2,000 participants across 7 countries. In the online experiment, participants from eastern (South Korea, Vietnam, India and Hong Kong) and western (USA, Germany and the Netherlands) countries — with ‘collectivistic’ versus ‘individualistic’ cultural background scores, respectively — were presented with an interactive simulation that explained herd immunity, a text-based explanation or no explanation. Next, either the social or individual benefit of vaccination was emphasized. Then, participants were presented with fictitious scenarios about two diseases that varied in their contagiousness (high or low), the available vaccine and the vaccine uptake in the community (42% or 62%). Following each scenario, participants rated their vaccination intention on a scale from 0 to 100, in which a higher number indicates a higher intention to vaccinate.

Participants from countries with a collectivistic culture (excluding India) reported higher vaccination intention than participants from individualistic countries, which was partially due to their collectivistic self-construal (the tendency to define oneself in terms of ‘we’ instead of ‘I’). Communicating the concept of herd immunity increased vaccination intention among participants from countries with an individualistic culture, but had no effect among participants from collectivistic countries. These results prompted the authors to conclude that prosocial nudges are particularly effective in countries that value personal goals, self-expression and individual rights and lack a prosocial cultural background.

Although today many people are familiar with the concept of herd immunity owing to the COVID-19 pandemic, in 2017 this idea of considering others’ benefit for health decisions was new and quite inspiring to me. Even though the role of risk perceptions for health decisions was widely recognized, emphasizing the social externalities of vaccination prompted a new perspective on health decisions that acknowledges the importance of social interactions.

“perceiving health decisions … as social interactions can motivate healthy choices.”

The benefit of considering the health of others can be applied to many other health behaviours, for which different direct and indirect mechanisms might come into play. Regular hand washing can prevent the spread of germs. The misuse of antibiotics for viral infections exacerbates the problem of antibiotic-resistant infections. Healthy eating might inspire others around you to eat a more balanced and nutritious diet as well. Thus, perceiving health decisions not as individual decisions but as social interactions can motivate healthy choices.