Vaccination on Invitation Only

How would you respond to receiving an exclusive invitation for getting vaccinated, that is send by a trusted friend? There has been lot of debate about who should be vaccinated first, so why not give the people themselves a voice in that choice: a real choice. This blog explores the idea of having people themselves decide who gets vaccinated first.


– How to use the insights from behavioral science to improve your health and wellbeing –

Reading time: 6 minutes

Getting people to vaccinate requires (1) correct attitudes towards vaccination and (2) correct behavior on the day of the planned vaccination. This requires communication with citizens at various times: both before and during the vaccination period. This idea mainly focuses on showing the correct behavior during the vaccination period and should therefore be part of other interventions.

The next person to be vaccinated will be introduced by you!

People with an invitation for vaccination can send an exclusive invitation to one other person over the age of 18 and thereby help determine who will be vaccinated next. The invitation says that the sender will be vaccinated and offers an exclusive invitation to the recipient to also plan a vaccination. Next, the recipients can then continue to send one other person an exclusive invitation to be vaccinated as well. In this way people themselves determine who will be vaccinated first. The recipient can accept the scheduled appointment or change it to a more convenient date and time.

Behavioral perspective

The idea of Vaccination on Invitation Only is based on various insights from behavioral science. First, the limited availability of the vaccine is used to make it exclusive. People often attach more value to items that are difficult to obtain. This is called the principle of scarcity.

The willingness to vaccinate in The Netherlands is currently around 70%-80%. If this had been 100% there would be no need to create a sense of scarcity. Then we all just have to wait for our turn. Because this willingness to vaccinate is not 100%, the principle of scarcity is used to make the vaccine more desirable.

Back in 1975, the psychologists Worchel, Lee, and Adewole asked people to rate chocolate chip cookies. They showed one group 10 cookies in one jar and showed another group two of those same cookies in another jar. The cookies from the two-cookie jar received higher ratings, thus showing that people attach more value to items that are scarce even when the items are identical.

Companies that use limited editions make good use of the scarcity principle to signal scarcity. Effectively, they are saying: you better buy it now, because it will not be available later. Magnum, for example, launched two new limited-edition flavors – Pink Raspberry and Black Espresso – back in 2015. However, as long as the flavors are successful, Magnum continues production of the ‘limited edition’ flavors, and I was still able to buy Pink Raspberry last summer.

Limited editions make good use of the scarcity principle.

Second, the idea of Vaccination on Invitation Only uses sender familiarity to increase trust. People may be more influenced in the decision to get vaccinated by someone they know well and who also gets vaccinated than by an abstract and anonymous government. The people close to us are more familiar and their opinion are usually in high regard. This is related to the principle of authority.

We often trust people we are familiar with on issues in which they are not experts. Take for example, Brazilian President Lula da Silva. In October 2012 Brazilian President Lula da Silva went public with his diagnosis of cancer, which he himself attributed to smoking. Da Silva is not an oncologist, but after Da Silva’s disclosure on his diagnosis, spikes in Google queries for smoking cessation were the highest ever recorded. They were far greater than similar searches made on World No Tobacco Day or New Years Day.

We often trust people we are familiar with on issues in which they are not experts.

Third, people copy the actions of others. If they receive an invitation, this means that the sender is also getting vaccinated, thus showing that other people are also getting vaccinated. When more people get vaccinated, this effect is amplified because (1) recipients will receive multiple invitations from different people and (2) invitation senders will receive more messages that recipients already scheduled an appointment. All this contributes to the image that most people actually get vaccinated. This is called the principle of social proof.

By the way, in case recipients already scheduled an appointment for vaccination, they should not be able to schedule two appointments. However, from the perspective of social proof it does make sense to send both the sender and the recipient a message to let them know about the fact that both of them already have an appointment. As said, this contributes to the image that most people actually get vaccinated. The send then has the ability send an exclusive invitation to another person.

The most famous research on social proof is probably conducted by psychology professor Robert Cialdini and his colleagues. They put three different signs in the hotel rooms of different guests (see figure below). The first sign served as the standard message and just reminded people to reuse the towels to save the environment. The second sign also reminded people of this program, but also revealed the actions of other people. They told people that 75% of the other guests in the hotel participated in the project. Finally, the third sign, specifically showed how many people that were staying in that exact room where reusing their towels. Customers who only had the standard message participated in 37% of the cases, customers who had information about the behavior of other guests in the hotel participated in 44% of the cases, and customers who had information about the behavior of other guests in their room participated in 49% of the cases.

Probably the most famous research on social proof.

Expected impact

The biggest impact of this intervention is that people have a say in who is vaccinated first. There is a lot of debate about who should be vaccinated first and this idea allows people to influence that decision personally. These people also stimulate other people to schedule appointments. The invitation for vaccination also contains a proposed time and date for a vaccination, which the recipient can change (or accept). This increases the chance that people will actually plan and keep their appointment, especially when an SMS reminder is send the day in advance.

Early adopters of vaccination often know other early adopters that they will invite, creating a snowball effect of early adopters inviting each other. This ensures that the people who are positive about vaccination are quickly vaccinated, quickly creating a large group of vaccinated people and contributing to herd immunity. This, in turn, ensures that people gain confidence in vaccinating, partly because they are invited by friends or family and party because they see many other people around them also getting vaccinated.

Finally, this intervention could provide increased support for the vaccination policy, because people can decide for themselves who is vaccinated first. It thus ensures that people who need the vaccine most – as judged by people themselves – get it first and ensures the most efficient building of group immunity.

Vaccination on Invitation Only Click To Tweet

Niels Vink (1975) is a behavioral economist and sports enthusiast. He has Master degrees in Social Psychology (Leiden University) and Industrial Design Engineering (Delft University of Technology) and holds a PhD in Consumer Behavior. He lives and works (out) in Haarlem.

Want to know how you can get your marketing, communication and sales in better shape? Drop me an email at

Source of top image: Tara Winstead



Leave a Reply