What is SocioVax?

The vast majority of the Dutch population takes part in the National Immunisation Programme (Rijksvaccinatieprogramma or RVP). That high participation rate is causative in preventing many people from becoming seriously ill and dying from infectious diseases. However, there has been a perceptible decrease in the number of people participating in the National Immunisation Programme. If people are not vaccinated in sufficient numbers, then the Netherlands will once again be facing more frequent cases and outbreaks of the diseases that are covered by the National Immunisation Programme. For that reason, it is important to understand why people choose whether or not to have vaccinations given to themselves or their children. What factors play a role in this choice? What differences do we observe between people, and how can we explain those differences? The National Institute for Public Health and the Environment (RIVM) is investigating these questions in the SocioVax research programme. SocioVax will also assess which approach is most effective for giving people accurate information and assisting them in making that choice, and how vaccination programmes can be offered in such a way that participating is as easy as possible.

What has already been researched?

The SocioVax research programme was launched in 2023. The first step was an exploratory qualitative study. It involved conducting interviews with youth healthcare professionals all across the country to learn about their first-hand experiences in implementing the National Immunisation Programme. In addition, a literature review was conducted to identify which determinants or circumstances play a role in choosing whether or not to be vaccinated, and in the decision-making process leading up to that choice. A literature review was also done to identify which interventions can contribute to increasing vaccination coverage.

The results of the literature review on the determinants of willingness to be vaccinated and participation in vaccination for the flu vaccine as well as the vaccines in the National Immunisation Programme have been posted online.

What research is still planned in the SocioVax programme?

The results of the literature review on effective interventions will be published in the course of 2024. At that point, the researchers will also share information about what care professionals from youth healthcare services (JGZ) are already doing in practice in the Netherlands to support parents and children in reaching a decision about vaccinations. That will be followed by the initial results from studies in conjunction with the parties implementing the National Immunisation Programme in various regions, including more information about local initiatives and studies aimed at gaining a better understanding of participation in vaccination and improving service quality for vaccinations.

Twice a year, SocioVax also conducts a survey on willingness to be vaccinated and various determinants of participation in vaccination. The first survey results will be published on the website in the second half of this year. The literature on factors related to willingness to be vaccinated and participation in vaccination will also be updated, as well as the latest insights on interventions and their effectiveness. The data will be published on the website as it becomes available.

What lessons have already been learned?

A number of initial lessons can already be identified based on the literature review and the research on determinants of vaccination behaviour and potentially effective interventions, and the interviews with youth healthcare services (JGZ). More information is available on the SocioVax website.

It was apparent from the literature review and the interviews with youth healthcare professionals that there is a great deal of information available in the field about effective use of communication. For example, various communication formats can be used to increase vaccination coverage. Our results based on a review of international literature suggest that a care provider who recommends vaccination directly, using such phrases as “I recommend that...” or “a vaccination is available for you”, can contribute to higher vaccination coverage. In actual practice in the Netherlands, the focus is more often on providing accurate information, rather than on giving recommendations, according to the youth healthcare professionals we spoke to during the course of our research. Another important factor in communication is the ease of access. Accessible communication needs to be aligned effectively with the target audience and can be deployed in various ways. The format of the message can be adapted, for example by making the information understandable at the language comprehension level of the target audience, and taking the background and culture into account. It is also possible to make use of key people: people who are trusted figures in a community or group in society and whose knowledge is considered authoritative, such as the pastor or imam, the GP or individuals with first-hand experience. Moreover, it is important to disseminate the information at locations where the target group is often present, such as childcare centres or schools.

Accessibility plays a role in communication, but also in the physical environment. It is apparent from the international literature that various barriers to access can affect vaccination coverage. Some of these barriers may be more personal in nature, such as not having much time or being unable to arrange transport. Other barriers are more closely related to the vaccination system or how it is structured, such as how easy it is to reach the vaccination site and whether a reminder is sent. Sending a reminder to get vaccinated seems to be effective in raising vaccination coverage among various target groups, sent in various formats, such as SMS, e-mail or letter. A reminder sent to the care provider that a patient will soon reach the next step in the vaccination schedule can also contribute. Vaccination reminders are already used in actual practice in the Netherlands, but minor improvements could be made. To improve physical ease of access, vaccinations could be offered at locations where the target group is already present on a regular basis. One example is offering vaccinations at school. The literature review shows that offering vaccinations at schools can contribute to increasing vaccination coverage (this was primarily found in literature about HPV vaccinations).

There are determinants that affect vaccination coverage, but involve less of a focus on interventions. This is often because, although they play a major role, it is difficult or impossible to change the determinants. One example is the influence of social norms: codified or unwritten rules that determine what is viewed as acceptable or expected behaviour within a certain group of people. Depending on the social norm, its influence may lead to higher or lower vaccination coverage. Research showed, for example, that parents who were deciding whether or not to have their children vaccinated often allowed their choice to be guided in part by the choices of others in their social circles. Although some determinants are difficult or impossible to change, it is important to maintain an accurate overview of their influence. A comprehensive overview of potential influential factors is needed to gain a proper understanding of vaccine uptake by various people, so that interventions can be aligned more effectively with various needs.

A combination of different approaches often works better than one single approach. One possible explanation for this is that decisions regarding vaccinations are complex, and various determinants can play a role. By combining multiple approaches, we can respond more effectively to all those different determinants.


The initial results of the SocioVax research programme offer more insights into the determinants that play a role in deciding whether or not to be vaccinated. It also reveals which approaches could be effective in supporting choices about vaccination and/or improving ease of access to vaccination. This gives us a better understanding of where there may be opportunities to further improve vaccination policy in actual practice in the Netherlands. See the SocioVax website for the full research results.